As noted elsewhere today, Vast.com is the latest entrant into the online classified ads space. It's interesting to see how all these sites are taking slightly different approaches, from Google Base, to Edgeio to Oodle and now Vast. Meanwhile, Craigslist keeps chugging along with its years-old business model and legacy technology. But we digress.

Vast is super web crawler site. It scours the web looking for structured or unstructured classified info. "It's more akin to how Google used to work, which is you leave your data where it is, and we'll find it,'' said founder Naval Ravikant. "And what we do which is hard is extract the structure out of unstructured data and make it searchable.''

Unlike some listings aggregators and crawlers, which rely on a relatively small set of high-value sites for their data, Vast crawls as much of the web as possible. There's a downside to this since it invites in the possibility of junk data. "That's the tradeoff,'' Ravikant said. But he says the vastness of the crawl (excuse the pun) far outweighs the downside.

Vast's approach is different from Oodle, which crawls a select set of sites. "They're aggregating 30 or 40 sites and getting a lot from those guys,'' Ravikant said. ''We don't feel that's sustainable because those guys are going to block you over time. They're going to view you as a competitor.''

And it's different from newly launched Edgeio, which hopes to scoop up specially tagged ads posted on blogs and elsewhere. "The problem with that is there are no results over there,' Ravikant said. "There's less than 20 or 30 classified listings per day put on blogs. (Ravikant added later that he meant individual bloggers, but that some classified sites use blogging software and produce more listings. - Eds) So were in the middle. We're going after real estate brokers, car dealers, job placement agents, small job boards, that kind of stuff. And we pick up the big sites also. And we pick up the small sites, as well.''

Vast is starting with three classified verticals - jobs, autos and personals. But other verticals will be added over time, bringing it up to 20 by years end.

Vast is not necessarily intended to be a destination site. Ravikant forsees other web sites making use of the Vast API to publish listings on their own sites. As for the business model, sponsored classified listings will eventually be added to the results.

The company has raised $5 million so far, and used "very little of it,'' so far, Ravikant said. The San Francisco company has 21 people, most of them overseas.

Mike Masnick at Techdirt has been asking an important question about the rush into the classified ads space, namely: "(W)hat hasn't been made clear is what problem these sites are actually solving. We hadn't heard of people complaining that Craigslist and eBay were too centralized."

Says Ravikant: "The majority of our results come from the long tail...from the thousands and thousands of sites you would never search yourself. For example, if you browse for car results, you'll see how many are coming from little dealer sites you would never know to visit or find...If you want to buy an iPod or a Mini that's easy with these other sites. If you want to buy that Alfa Romeo from 1967, that's hard. The value to the end-user is the long tail.''