KoeN only got on facebook cos of planetarion people bugging him :P
I can see a few issues with this.
Firstly, hands up who has any idea how to make facebook apps? I don't :P
Secondly, giving out rankings on facebook makes it pretty much instant for people to find out your co-ordinates. This would be the same with having personalised banners for the current round. I'm not sure how many people would accept this (though these days some people seem more relaxed about their co-ords than in the past).
Finally, I'm not sure it'd be possible to play planetarion via facebook at all without coding an entirely new frontend for it...and they'd have to act with a security layer over the database... it'd be pretty complex
