If ever there was a case for parental controls, it's this: According to Virtual Worlds Management, there are now over 200 youth-oriented virtual worlds live, planned, or actively being developed. In other words, rather than grab a ball and glove after school, kids left on their own with access to a computer will literally have hundreds of virtual worlds to choose from and plenty of opportunities to spend their allowance.

When broken down into worlds targeting kids (7 and under), tweens (8-12), and teens (13+), VMW says "the kids market is the clear leader," noting 107 worlds are banking on at least part of their audience consisting of kids in the under-7 range. To make money off these markets, 59 of the virtual worlds use micro-transactions, giving users free access to the world but charging for virtual goods. Another 57 worlds follow the subscription based model, and 46 use advertising, VMW says.