[ryandrake]

I've never seen one that actually works. It seems like whether or not I check them, the next time I log into [every site] I have to re log in.

[zahlman]

Really? I don't think I've ever seen one that doesn't work. What sites are you using where you encounter this? Have you checked your cookie settings?

[userbinator]

Seconded. Your browser is probably set to clear cookies on close.