Facebook launched their developer platform back in May 2007 to some serious applause from geek types the world over. The Facebook figures on usage of the Platform since that date are impressive - at the Future Of Web Apps conference last week, I went to a session with Dave Morin, the Platform manager. Apart from the 43 million users, 50% of whom return daily (enough to make you really sweat..), he also said that there are now more than 5,000 applications built on the Platform - in only 3 months. More interesting is that over 80% of users have added a Facebook application to their profile.

Doing the maths, I reckon that means: 0.8 x 0.5 x 43,000,000 = 17.2 million users using Facebook applications, which if averaged out across the 5,000 (bad assumption, but go with it) means each one has over 3,000 users. That's 1,000 users a month - a pretty impressive take-up rate, especially when you consider that the audience isn't a bunch of developers but Joe and Joely public...

Morin talked about how "growth, engagement and monetization" were the three phases in the development of any web application and that Facebook was quickly sidestepping the first two and beginning to enable the third.

Whether this is true or not, the (at least partial) opening up of the social graph is obviously hot news.

So. That's presumably why MySpace is doing the same thing - with a formal announcement expected next week. It'll be very interesting to see what this means for Facebook, who have had all the column inches recently. The battle over the true opening up of the social graph to the outside world (and not just to the Platform itself) could be a future battle. For now, it'll be interesting to see what difference - if any - this makes to the battle of the social networks...