While the benefit of learning the technical skills and such is by default a given, spending hours and hours on a computer isn't good.

"They are learning how to communicate online, craft a public identity, create a home page, post links."

Crafting a public identity? I think it's hard to say this is "good", seeing as it's never been possible to do before now. Also, spending hours and hours on myspace, I would argue, is actually more detrimental to a child's social skills and real life skills than not.