I think Facebook itself has the memory leak: I never leave it open for more than about an hour at a time, but I've heard from people that leave it open for days

I think Facebook itself has the memory leak: I never leave it open for more than about an hour at a time, but I've heard from people that leave it open for days that it can take up between 1 and 2 GB; some of these people use Firefox, some Chrome and some Safari.