Sharing what mobile apps you have in a social network has been tried various ways. Appsfire hit on the idea of socialising apps.
Zwapp is coming at it from a slightly different angle. Its iPhone app (iTunes link) auto-discovers what apps you have on your iPhone and connects up your contacts, Facebook and Twitter friends. You then follow people who’s opinion’s you respect when it comes to apps. It even has a live feed where you can see what apps your friends are using and downloading (privacy is now most definitely over it would seem).