In late May social networking site Facebook launched a platform that effectively opens the site up to third-party developers. The platform allows the creation of Facebook applications ­ plug-in extensions for the site that can interact with users and access the information stored in user profiles.

Within days hundreds of Facebook applications had been launched, some of which have become massive successes, drawing in tens of thousands of users. At the time of writing there are 2,290, and the number is growing every day.

The growth of the user base for some applications has been so rapid that Facebook has even had to introduce measures to slow their viral nature, and set a limit of 10 user invites a day. This means that a Facebook user can’t invite all their friends to one application at once, angering some developers but calming the initial flurry of arbitrary invites that threatened to descend into spamming.

The speed with which so many widgets were launched is an indication of how low the barriers to entry are for Facebook applications. A talented web designer or information professional should have little problem creating a simple application, and all widgets have the same chance of success on the site.

Applications range from the funny but useless to fully fledged information services. Some are surprisingly well featured because they can access information stored in a user’s profile, and collect more information with a graphical interface.

The Facebook application programming interface (API) even allows integration with third-party websites and desktop applications, so a service doesn’t have to start and end on the Facebook site. Likewise, a developer’s own database can be used by a Facebook application.

There are many opportunities for information-based companies or information departments to get involved in the phenomenon. For example, property companies are creating Facebook applications that tie into their own database of rental properties to create searchable property lists; their next step could be to use the location information in a user’s profile to automatically narrow the search, and alert the user to available apartments in their area.

Jobs in your lap
There are also job agencies that allow users to search for vacant positions, although here too there are more intelligent possibilities. User profiles store such useful data as address, job history and education, and job search applications could use this to target locations and types of job, displaying appropriate jobs as soon as a user opens the application.

Some applications even let users act as headhunters by referring their friends to jobs; the agency pays a finder’s fee if a successful candidate is put forward. This is a good example of using crowd-sourcing rather than clever coding to do the matching, although it might be viewed by some as spam. Either way, it’s an approach that would require a careful reading of the terms of service.

It’s not just companies with large repositories of searchable information that can capitalise on the Facebook APIs. More generic business applications can also provide a simple but vital service.

PayPal, for example, has developed an application which allows users to easily make payments to other Facebook users. PayPal earns a percentage revenue on any transaction, and by getting into the market so early it could become the de facto payment option for Facebook. It’s probable that it will be incorporated into other applications, such as the job agency service that pays a finder’s fee to headhunters.

But applications don’t have to provide a useful service at all to become profitable or popular.

Catch the bug
Viral applications, such as maps that display which countries a user has travelled to, have become popular. If a travel company developed such an application, it could be a platform for selling plane tickets or hotel reservations. Alternatively, a handy currency converter would be the ideal place for a bureau de change to advertise its services.

It’s this kind of innovation that is important. A useful application will become popular, but so will an interesting one. Going viral isn’t a predictable target, but you can maximise your chances by making your widget interesting, useful or, even better, both.

One particularly interesting application comes from Dell. It allows a user to build a virtual PC on the Dell website, and place a contributions widget on their profile. Friends and family can then make donations to buy that computer for the user. This effectively places a free advert for Dell on user profiles, driving traffic to its site. It also sells a PC for the company, and creates a buzz around the brand.

As well as allowing integration with third-party sites, the API also allows users to interact with Web 2.0 sites from within Facebook. Mini-blogging tool Twitter, for instance, has an application that lets you update your status from within Facebook. And calendar and events site Upcoming has a widget that lets users broadcast a list of events they’re attending. This interaction not only provides a service, but acts as an advert for those websites.

Any application that becomes popular on Facebook takes users and traffic to the original site, and increases its user base. It’s another value-add, and demonstrates that an application doesn’t have to be successful in any tangible financial sense in order to be beneficial for a business. Considering how low the barriers to widget entry are, it makes perfect sense.

Facebook provides two languages to help create applications: FQL and FBML (in effect, Facebook-specific versions of SQL and HTML). FQL lets you access data held in user profiles, and FBML lets you create the look and feel of the application. It is also possible to use Javascript, but it behaves slightly differently on the site than elsewhere.

Facebook has a developer’s website, with good documentation and a downloadable development environment in which you can write applications. It’s by far the best place to start for programmers interested in developing for the site.

Developing an application is not the only way in which Facebook could prove useful to your business. After all, the social networking website itself was created as a social tool, and employees could find it valuable as a communication and collaboration tool. This is how students and academics have been using it for some time.

Also, if a company creates an application, then a good way to start a buzz around it would be to register employees with the service. It is often hard to get the first few hundred subscribers, until word of mouth gets out, so having staff on Facebook could be very useful.

Campus dream
The academic opportunities for Facebook are huge. The site has its roots in academia ­ it was initially conceived as a social tool for students ­ and despite opening up to all users it still has a very large academic bias. But there is more Facebook can do other than just allow students and teachers to chat.

Facebook has a Courses feature, which lets people in the same class talk and share information, although this is being phased out in the hope that third-party developers will fill the void with a better-featured version or, more probably, several.

Collaboration services are a very large part of academic life now, and a large industry. A very well-featured Facebook application that provided the same functionality would be enormously popular.

There could be various options for monetising such an application, such as a deal with Facebook that involved sharing advertising revenue or simply charging for the application, although this is so far unprecedented.

Virtual Bookshelf is an application with obvious appeal to students. It allows you to upload a list of the books you are reading, compare notes with other people who are reading those books, and recommend books to each other. This could allow students from various universities to talk to people studying the same subject as them and reading the same books.

Language exchanges are another academic possibility, and already several applications have emerged that allow a user to search for someone who is willing to trade language tuition.

The fact that this extension of functionality is available on Facebook, rather than another popular social networking site such as MySpace, is helpful. The Facebook platform is more regulated, and its user profiles are far simpler to extract data from.

Initially, Facebook sign-ups were limited to those with an academic email address, and even now profiles remain more honest and accurate than those on MySpace. The site even stores semantic information about the relationship between contacts, which could allow some very powerful applications to emerge.

So far there has been a huge number of applications, but none that utilises the site to anywhere near its potential. The first to become truly useful and profitable will be the ones that learn to exploit the wealth of information available.