I'm used to this set up and not a problem if they often ask for my login details everytime I open a browser. In fact, I prefer this one rather than keeping myself logged in on the particular site (even for other users it is convenient) just to save time and hassle. However, it's a different thing if i'm already logged in, then I hit the backspace or check their other features then they will ask my login details once again even i'm not closing the browser, well in this case it's hassle and annoying even it's for security checking.