After the big SSO update yesterday on TD.W, It seems ti be the only site I can log into physically, and GA.W uses my username from there now. My karma transferred from there to here...
I personally, do not like the thought of having my accounts linked together. I expected to remain an anon in both sites, this appears to be a break of anonymity.
Not really a safeguard. Nothing stops them from just coming to the other sites and looking for your same username and seeing your history.