Even financial sites can play the Web 2.0 game. TheStreet.com (NASDAQ:TSCM) recently announced its acquisition of Stockpickr.com, a fast-growing site that recommends stocks based on its users' interests, as Netflix (NASDAQ:NFLX) does with rented DVDs.

TheStreet.com already owned 49.9% of the site, so it was really just a matter of time before it swallowed Stockpickr whole.

Naturally, TheStreet.com isn't the only financial site making the most of what former Fool Jim Surowiecki calls "the wisdom of crowds." Head over to Motley Fool CAPS, and you'll see that wisdom (or Foolishness?) in full force.

CAPS offers its nearly 29,000 members the opportunity to rate as many as 4,409 different stocks. Each player's performance is stacked against everyone else's, yet CAPS is billed as a stock idea service, because players can also ferret out new ideas from the picks of like-minded investors.

Even Dow Jones' (NYSE:DJ) MarketWatch has gotten in on the fun from time to time, holding online stock-picking contests.

It's common sense, really. Investors can be a passionate lot, displaying amazing levels of fandom and dedication when money is at stake. On some of the more heavily populated Yahoo! (NASDAQ:YHOO) discussion boards, you'll see fierce bear and bull arguments that make the Red Sox-Yankees rivalry seem like a mild squabble.

You could argue that financial sites were Web 2.0 while Web 1.0 was still in fashion. Community-driven discussion boards have been around longer than online financial newsletters. However, technology has evolved to make that engagement more useful. Sites like Stockpickr and Motley Fool CAPS reward your interaction by suggesting new ideas. The more you participate, the truer your picks become.

I'm glad Reed Hastings made that model fly with Netflix. But in all honesty, I'd rather know my next great investment than learn about the next great indie DVD.

Netflix and Yahoo! are Motley Fool Stock Advisor newsletter selections. You can learn more with a 30-day trial subscription. And if you want to get to know yourself a little better, give Motley Fool CAPS a try, too.

Longtime Fool contributor Rick Munarriz thinks that he was Web 2.0 even while Web 0.0 was cool, but that's only a matter of opinion. He does own shares in Netflix. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.