Local search today is in the state that web search was in, pre-Google. There are lots of Yahoos and Altavistas, but no Google (Yelp is so reminiscent of Yahoo web search).
Foursquare still has a long way to go before it can consistently give better results than Yelp, but this is a great start! Hope some startups get inspired by this and realize that local search is not a dead problem to work on!
Heck, it's in the same state it was post-Google, too, when Citysearch was the disruptor. Yelp started out good, probably very akin to where Foursquare is now (clean-ish data, fresh perspective), but tolerated too much garbage, much like Citysearch did, until the user has to over-engineer their search in order to get relevant results that aren't contained in 400 pages, 5 items per page.
Think of how long it's been since Yelp added any filtering criteria. Take a look at their user-photo gallery functionality. Old, stagnant, and ripe for a new generation. However, since sites have been repeating these mistakes for 15 years, there's no indication that any of these are solvable problems.
Foursquare still has a long way to go before it can consistently give better results than Yelp, but this is a great start! Hope some startups get inspired by this and realize that local search is not a dead problem to work on!