It does make a case for not using common user names. I used to always try to use my first name in the early days of the Internet, but it was almost always taken.

The one time I got it was with one of the Maxis online accounts and for the next couple of years I seemed to get a bunch of password reset requests from people who thought it was their account.

While there's something to be said for not using the same user name across different systems using a very common name is not a mistake I'm going to make again.