Tim O'Reilly, who gets credit for coining "Web 2.0," has taken several whacks at defining it, and he took another one this week at his own Web 2.0 Expo this week in San Francisco: "We are talking about persistent computing in which we are becoming part of a great machine." Thanks, but if that's it, I'll pass. If you, gentle reader, on the other hand, want to plug into whatever Web 2.0 means, a ratings company called Hitwise used the conference as the launch platform for its own little bundle of hype, a list of six products and companies that it thinks will rise to the top of the Web 2.0 heap. See if you agree.Hitwise is a click-counter that measures traffic to more than 800,000 Internet sites. Based on its numbers, it announced this week six Web 2.0 companies most likely to reach the soaring success of YouTube, Wikipedia or Flickr. (Are you already getting the idea that Web 2.0 may have as much with market valuations as innovative technology?)

These products are supposedly what O'Reilly has in mind when he says of Web 2.0, "Web 2.0 is the business revolution in the computer industry caused by the move to the Internet as platform, and an attempt to understand the rules for success on that new platform. Chief among those rules is this: Build applications that harness network effects to get better the more people use them."

The people, Hitwise concluded, are most likely to be early adopters, so it looked at the sites users it defined as early adopters are already visiting. These six, it predicts, are sites that the rest of us will soon be using, too:

• Imeem -- Be an even bigger fan of Kirsten Dunst in "Marie Antoinette," or push your playlist of 7 Sharp 9 favorites. Just share the heck out of what you care about most.

• Piczo -- Build your own Web site just the way you like it -- if you like the piece parts this site provides (and if you like the parts this site provides you're probably a teen-ager, because that's what everything about this site is carefully designed to look like.)

• StumbleUpon -- Sometimes this community thing is just too hard. But StumbleUpon is designed to make it easy. Rate the Web sites you . . . stumble upon . . . for your friends. What could be easier? You don't even have to watch 20-minute videos of guys who are supposed to look like Colin Farrell. Rating Web sites may not be the most significant use of your time, but at least it's an easy way to be Web 2.0.

• Veoh -- Videos. More videos. Videos you like. Videos you don't like. Videos your friends like. Videos people you don't know like. Videos people you don't like like. And like that.

• WeeWorld -- Create a cartoon of yourself -- or the self you'd like to people to think you are -- then use it as your icon on your other Web 2.0 sites. Even easier than carving up a screen grab from your favorite game.

• Yelp -- A Facebook for hardware stores? A community guide by a community. When you get tired of rating your music, rate your shoestore. (And then rate your fellow raters?)

If you're thinking some of this doesn't sound exactly blindingly novel, you're not alone. No less than Tim Berners-Lee, who invented Web 1.0, the real World Wide Web, was asked last fall to agree with the distinction that Web 1.0 is about connecting computers, while Web 2.0 is about connecting people. He didn't see it that way: "Totally not. Web 1.0 was all about connecting people. It was an interactive space, and I think Web 2.0 is of course a piece of jargon, nobody even knows what it means. If Web 2.0 for you is blogs and wikis, then that is people to people. But that was what the Web was supposed to be all along. And in fact, you know, this 'Web 2.0,' it means using the standards which have been produced by all these people working on Web 1.0."