I've just noticed that someone can Google my name and instantly know If I'm on Stack Overflow, because it shows the "seen 6 minutes ago." It's shown on the results screen, the searcher doesn't even have to click the search result.
Aside from having respect for Google search and feelings of joy for Stack Overflow getting good ratings there, I find it a bit "big-brother" creepy.
Why do we need "last seen," anyway?
At a minimum I'd expect it to keep track using dates, not exact times. But it should be removed altogether.