Not actually Digg, but a Facebook application like Digg, but for photos on Facebook. Facebook apparently has the most photos anywhere on the web — there should be a button under each allowing users viewing them to rate them (thumbs up/down; or rate 1-10; or click a ‘LOL’ vote to vote up the funniest pictures). Then the main page of the Facebook app would show the top rated (and funniest) photos of your friends; as well as the ones your friends voted top (which could be photos that don’t have your friends in them); as well as the top photos (funny and top rated) by the entire Facebook network.
Update: The widget on the user’s Profile page could show a random photo from their collection; or it could show thumbnails of the ones people have rated funniest, or top rated. Or it could show photos across Facebook that the user’s profile you’re viewing, has rated funniest or top rated.
Question: I know you can get access to photos via FB dev platform, but I’m not sure what restrictions/privacy there is — if any. I would think you could only view photos shared by your friends???