Yelp COO Geoff Donaker, subbing at the last minute for a “very ill” CEO Jeremy Stoppelman, told an SF Connect audience that Yelp’s base of 24 million + unique “Yelpers,” 7 million reviews and “thousands” of advertisers represents a rich opportunity for any vertical small business — including Realtors.

Although Yelp takes a horizontal “lifestyle” approach to business categories and doesn’t break out real estate per se, if Realtors “spend 20 minutes to fill out a profile, they will see an uptick in business from Yelp,” said Donaker.

Donaker noted that Yelp now has an active presence in 28 local markets in the U.S., the U.K. and Ireland. The service is not likely to be profitable for the full year in 2009, and may not be in 2010 either because of continued investment in the business, which constitutes three full floors of a downtown San Francisco building and another large office in New York. Things are going well, however, although selling the company or going public is not a “near term focus,” he says.

Looking forward, Donaker says the internally produced features constitute a rich (and free) toolset for businesses to use. Products are added based on what customers want, he says. The iPhone app has been especially well received, and mobile, in general, now constitutes about 5 percent of Yelp’s usage. Video, however, is not a high priority, with fewer than 10 percent of businesses saying they’d like to use it.

The site’s reputation for fostering negative reviews is mostly unfounded, adds Donaker. Eighty-five percent of reviews are three stars or more (on a 1-5 basis). Seventy percent have five stars. Just 15 percent have fewer than three stars.