I’m a firm believer in encouraging students use psuedonyms on the web, at least while they find their feet in social media. I wouldn’t want to be haunted by my freshman composition assignments for the rest of my life, and accordingly I don’t think it’s fair (or smart) to encourage freshmen to blog under their own name until they develop some sense of what they want their identity to look like long-term. (Some are ready earlier than others, but it must be a choice).
I generally encourage pseudonyms as a transitional step. This approach also keeps FERPA issues at bay. But the process of finding a usable name takes forever, and students end up choosing pseudonyms that generally are pretty traceable to them.
This Random Username Generator is a great way to have your students generate random names. Not only are the names it generates meaningful and memorable, but click one and it will run out and check its availability across a number of platforms.
You’ll still have to remind students to use good taste (I’m not sure the randomly generated “codpiececurry” is the best moniker, for example), but it should radically simplify those first steps for your students, keep their identities under their control, and provide a bit of fun in the process.