Kinda interesting but I wonder if it is normalized at all for the yelp review density in a given area. See xkcd: http://xkcd.com/1138/ as I draw some unusual correlations in the Boston maps.
Either answer should give a valid measure of regional hipsterdom. Is it just hipsters that use Yelp? If so, go where they're reviewing. If not, follow the hipster tag. I can certainly vouch for the validity of the London version, that's for sure.
Strangely enough "hipster" doesn't quite line up with heat maps for other words in SF, NYC, and Philly.