I predict the virtual 'wars' to come will be like the browser wars. Walled gardens will whither under the same pressures that browsers felt. That's my (somewhat safe and obvious) prediction.
Some interesting discussion today on the merits of SecondLife versus Croquet. Certainly, it's a big space, and each may fill a different niche. I'd say at this point there is no safe money, so look at all the options.
Here's an interesting bit from Slashdot that friend sent me..
"Having already taken the timid steps of open-sourcing the code for its client software, Linden Lab has confirmed that they'll be going the whole way, and will soon be opening up the server code for Second Life. This furthers Second Life's ambitions to be a fully distributed 3D network — built on interoperability and not owned by one company — a bit like the Internet itself. ZDNet's The Social Web asks: 'who will be the first to offer Second Life hosting or use the server code for their own internal purposes? IBM would be an obvious candidate, perhaps offering corporate Second Life services. And for the rest of us? GoogleLife, free virtual land — ad supported of course. It's certainly a possibility.'"