This is amazing stuff. It's animated four-square check-ins, mapped, and animated. It really brings the work of Bill Hillier to life:
Foursquare check-ins show the pulse of New York City and Tokyo from Foursquare on Vimeo.
Open data. It's the new frontier in how we understand how cities work. Because until this increasingly bleeding edge, we were bloody clueless. The 20th century wiped the collective memory and it's all a clean slate.