There are a few problems with this as implemented in Google+. (Correct me if I'm misinformed, I haven't been able to keep on top of all the new news.)
EDIT: I made some wrong assumptions, particularly about how your Google accounts are tied together, see Matt's reply below.
1) The rules are apparently not being made clear. If I see "no shirt, no shoes, no service" on the entrance I know exactly what that means. When you sign up for Google+ I'm pretty sure it doesn't say "Upside down characters and offensive names will lead to all your Google accounts getting irreversibly banned." Maybe there's some language buried in the TOS. That's not good enough.
2) Google is changing the rules (or enforcement of the rules) late in the game. If someone has had a Gmail account for 5 years using a pseudonym and Google just now decides to lock them out of it when they try to sign up for Google+, that is Google's fault. At least warn them of the offense before banning or prevent them from using Google+ while still allowing access to their Gmail.
3) No recourse. I know Gmail is a free service, but people still use it for registering on financial websites and priceless family correspondence. It is tied to someone's identity. Google needs to have a well defined and timely path of recourse for people who get banned for minor offenses. Directing all customer support requests to /dev/null is not acceptable.