Mathew Ingram argues that Facebook is about fun, and that it's not that hard to turn a profit on a platform that's oriented around fun and games. He's certainly right that fun and business aren't incompatible, but I think it's a mistake to discount how useful it can be. In my experience the most useful features are not the add-on applications but the basic features built into Facebook itself. These features aren't as glamorous, but I think they're enough to ensure Facebook won't prove to be a fad like Friendster did
First there's Facebook's groups feature. Twenty years ago, people who wanted to organize to achieve a common goal -- whether it was supporting a political candidate, protesting a company's bad customer service, or finding other fans of a favorite TV show -- frequently didn't have a cost-effective way to do it. The phone and email were just too cumbersome and expensive. Even ten years ago, group formation required setting up a website or creating a mailing list, something that still required a non-trivial amount of work and often had limited functionality. In contrast, groups on Facebook are incredibly easy to create and maintain and they have a ton of useful features. The modest improvements in ease of use aren't amazing from a technical perspective, but they've made a big difference in peoples' ability to quickly form groups and find people with shared interests or goals.
Second, the photos feature on Facebook is incredibly useful. Of course, sites like Flickr have done photo sharing for years. But having its photo application embedded in a broader social network gives Facebook key advantages that its competitors can't match. If my friends have Flickr accounts, I don't know about it, but I can easily see which of my friends have Facebook pictures. The pre-existing social network also allows Facebook users to mark themselves or their friends in photos, which causes them to show up in their friends' photo albums.
Finally, I've been noticing that Facebook is beginning to displace Evite as the preferred vehicle for party invitations among my friends. This is another case where having a pre-existing social network is a huge advantage. With Facebook, I can create my guest list simply by running through the list of friends and checking the ones I want to invite. With Evite, in contrast, I have to dig up the email addresses of all the people I want to invite. And many people are already visiting Facebook regularly, so it's less annoying to RSVP there than on a site that only does party invitations. Adding an invitation feature to a site people already use creates a lot less friction than asking them to sign up for a totally separate invitations site.
All of which illustrates a point Clay Shirky has made: really interesting social changes are the result not of new technology, per se, but of social density: a networking site that 90 percent of your friends use is vastly more useful than a site that 10 percent of your friends use. Very little of Facebook's functionality is new from a technical perspective, but Facebook (and MySpace) are the first sites to reach a point where almost everyone in certain social groups use them. And that fact dramatically increases their value. I don't know if Facebook is worth $15 billion, but it's certainly not a flash in the pan, and its appeal isn't limited to Scrabulous.