I heart Steven Johnson; he's a good and interesting writer.
His latest book, The Ghost Map, is about the Broad Street cholera outbreak, which is one of my favourite London stories, always retold to friends in the John Snow, or as I walk past the pump.
Anyway; he's launched an interesting fuzzy geolocation service, outside.in.
Lovely, but it hasn't heard of Clapham, or SW8 3JF.
Come along now, the internet is not just for 'mericans.