Citysearch, Urbanspoon start pulling in tweets. Take that, Yelp.

Citysearch and Urbanspoon, two IAC-run sites devoted to helping people find places to go out and eat, are announcing deep Twitter integrations today. Citysearch will let businesses claim and manage their listings on the site and tweet from them. At the same time, both CitySearch and Urbanspoon’s pages will pull in tweets mentioning a business’ official Twitter name, letting visitors see and interact with a real-time stream of opinions about the place.

Now incorporating a Twitter stream isn’t jaw-dropping from a technical perspective, but it should serve as a warning to other review sites like Yelp that real-time streams of thoughts could pose a threat to their model. Citysearch also added Facebook a year ago, as one of the social networking company’s first partners for Connect. But Compete suggests that Yelp’s traffic passed Citysearch’s earlier this year in terms of unique visitors.

Citysearch says its Twitter features will become more sophisticated over time and the company may use sentiment analysis to determine overall ratings from a stream of tweets.

“Twitter has changed the norms of blogging and reviewing and these things together let us promote a use case where consumers can add and read content quickly,” said Kara Nortman, a senior vice president of publishing at Citysearch.

Instead of reading static reviews, people could check in on a Twitter stream to see if restaurant customers from the night before were happy with dinner. Or they theoretically could use a location-based service like Gowalla, Loopt or Foursquare to see if a bar is really busy right now based on the number of check-ins.

Citysearch’s move also comes as Twitter is on the cusp of launching paid commercial accounts including analytics and premium features for businesses that want to manage their presence on the microblogging network better. Nortman said while Twitter has grabbed mindshare and traction, it doesn’t have the same kinds of longstanding relationships Citysearch has established with local businesses through its sales force. She said Citysearch could help lend that muscle to the fast-growing startup, which recently raised $100 million in its latest round of funding.