Facebook does strike me as genius for one thing, though – being the first social network with no one specific social object something I initially talked about back in 2005, but being completely flexible about it.
Social object is the main thing the social network is about. Flickr has photos, Last.fm has music, 43Things has activities, Twitter has social statuses.
Through the facebook API, they’ve managed to allow external developers to inject any social object into Facebook. A few examples would be the applications to track movie tastes, music tastes, photos, etc. Now that is smart – I’ll go as far as saying Facebook wouldn’t be 1% as interesting if it wasn’t for that.