Has this been done yet?

Timeout London blog has this link to a site which collates lots of freely available public data such as Twitter feeds, Instagram etc and chucks it all onto a clickable map.

So far I’ve only seen your usual inane rubbish, but I guess it shows how freely you can get hold of what perhaps some people don’t realise has such a wide audience.

http://wearedata.watchdogs.com/start.php?locale=en-EN&city=london