I’ve come to the conclusion that it’s fundamentally impossible to predict which Web 2.0 ideas will take over the Internet. That lifts an incredible burden from my shoulders — I used to think it was my job to predict those things. Now I know it’s not my job — and, moreover, it’s an impossible task. So I can just sit back and marvel at the creativity that goes into coming up with various business models. Here’s three we discovered recently, two of them in today’s news:

• Jellyfish.com makes a game out of online shopping. Jellyfish uses a business model called “smack shopping,” in which merchants put a product up on a page and start the clock running. As the clock runs, the price on the product goes down, down, down. If you’re a consumer, you want to wait for the last possible minute to buy, to get the lowest price. But supplies are limited, so if you wait too long, you’re out of luck.

• Ning is looking to compete with MySpace and Facebook by allowing users to build their own social networking sites, providing tools to share videos and slide shows, publish music, and post blogs. Instead of becoming part of someone else’s site — another space on MySpace or face in Facebook — you can create your own.

• Dandelife is a new service that’s sort of like blogs, except it’s designed to allow people to tell their stories and biographies using text, pictures, and images, and it keeps track of the past using timelines.

Now here’s my guesses on how things might come out for these companies:

Jellyfish sounds like a great idea, combining the suspense of an eBay auction with the satisfaction of watching prices go down, rather than up. On the other hand, there’s no barrier to entry. If this is such a great idea, why isn’t eBay doing it already?

Ning: Their main selling point may prove to be completely unattractive — people like being part of MySpace and Facebook, and Ning may find that a private-label social networking service has no attraction at all. Nonetheless, if Ning proves to have the best, easiest-to-use tools, people will come to it.

Dandelife is a big question mark; I’ll know more about them after I meet with them Thursday. Dandelife looks like it may offer a nice complement to blogs, which are inherently ephemeral things. Mostly, that’s as it should be, especially when it comes to the vast majority of blogs, which are friends-and-family blogs. What you did on Sept. 1, 2001 is of little consequence, but your descendants a century and a half in the future will want to know what you did 10 days later.

What’s the most intriguing Web 2.0 startup you’ve seen recently? Write in below and praise the startups with great ideas. Don’t forget to make fun of the lamers, though, because how can we enjoy life without ridiculing the less fortunate.