Urban city guide Yelp, which helps its roughly 100+ million monthly unique visitors find places to visit (shop, eat, etc), has released a rather interesting feature that identifies keyword and phrase patterns in reviews.
The system essentially provides a heatmap (see below) for the density of keywords used in Yelp's reviews (39 million reviews have been contributed to the site by the way). While it's not exactly a useful feature for identifying actual places related to those keywords, it does accurately show the neighborhoods (which in large cities is important - particularly for tourists who aren't familiar with the local hotspots).
We took Yelp's Wordmap for a quick spin and found, for example, that if we were in the mood for a PBR (that's beer, well beer-ish) with some fellow hipsters, we'd definitely head over to Wicker Park or, more likely, Logan Square - a hotspot so to speak of PBR guzzling hipsters. Yelp was right on the money in this scenario for our test.
Wordmap is currently limited to fourteen cities but it's definitely not difficult to see how the system could be used in the future - by Yelp users, advertisers and merchants.