back in december last year, we introduced api v2 [1]. it was an improvement in almost every way from v1 of our api, which had been active since early 2009. we took everything we'd learned since the start of foursquare and with our use of v1 and put all that thinking into the new version.
when we announced v2, we didn't specify exactly when we'd turn off v1. we wanted to make sure we gave you enough time as well as wait for our own apps to go live on v2 (all our official apps run on v2 now).
so, we're finally sharing a date when we'll shut off api v1: august 1, 2011.
naveen