That's not the only weak link in that strategy. On the top of my head, patterns come to mind. The date/times you do - whatever questionable activity - you're doing, the way of doing it(say, your unique words, posting style, etc) all create a unique fingerprint of you. All they have to do is match it with your logged in(Google,MS,etc) data habits.

I guess the best way to be anonymous is to be schizophrenic.