I think Sylvia's Ten to ask - How to predict the Web 2.0 winners post misses the point. If you're experimenting, use whatever you please. Just remember you're experimenting. If you're implementing something serious, you should only be considering commodity services from big companies (GMail, Blogger, Flickr...). That is, you shouldn't be predicting winners, you should only consider things that have already clearly won. If you really want to get out on the edge and, say, play with virtual worlds with your kids, just remember that we're still in the AOL vs. CompuServe days there. It really doesn't matter which one you pick because they're all going down in what is the long run in technology terms, but near future in educational time.