A couple clues on where not put your investment dollars -- even if you get the chance.
There are just so many startups cropping up that do the same thing (see this Web 2.0 list) that one would have to really, really smart to pick the winners -- and most of us aren't.
A handful of excellent companies will surely emerge from the Boomlet. And the ones Yahoo or Google or Microsoft haven't gobbled up will go on to become successful publicly traded companies with real customers and business models. But there's a lot of "build it to flip it" going on. Mere greed is not a business model.
While only slightly duller, look at which companies who already have a large online footprint are the quickest and most adept at adopting the technology underpinnings of Web 2.0 companies. They are the ones most likely to be winnes on the innovations of dozens of startups that will fall by the wayside. There's a an arm race wtih Google, Yahoo and Microsoft most easily coming to mind.
Who are the others?