Yeah, Google web apps must have some scary Javascript bloat going on. I remember when GMail was lightning fast; now it takes 5-10 seconds just to load the first page of my inbox and chat windows.
Plus I can, you know, close the tab. One of the worst things about these enormous "javascript applications" is the high startup time (remember how much we hated Flash intros with loading screens?) that leads to leaving the tab open, which means that tab's disgustingly-high memory use is a constant rather than only occasional cost (I'm looking at you, Asana!)