Thats a big money question if your are a Qype insider. First you should know that SEOMoz consulted on the Yelp SEO strategy. Secondly you should know that Yelp and Google have a very close yet tumultuous relationship. Google indexes the Yelp site often and thoroughly. However I see no indication that Google favors Yelp pages in search results over other sites. That said Qype seems to have some page loading issues that could hurt its rankings. The pages need to load much faster. It looks like overall Qype has done a good job with SEO and has millions of backlinks.
I am not familiar with Qype but one of the best SEO boosts would be to optimize how it provides business owners with Qype widgets and badges that the owner can put on their own websites. The way these widgets and banners link back to the Qype is critical - The badges and widgets should use unique custom anchor links for text links or similar text in alt tags for image links. If Qype has not optimized these badges and widgets properly they could be missing out on a huge increase in traffic and rankings.