That question came up to me, when recently working on one project I needed to restart my PC several times. And therefore, while I used 3-5 web apps I needed to log back in to each one of them again, after each restart. And I started wondering if privacy-wise that auto-clear feature is worth it or not? Has anyone maybe tested that?
I use two browsers. One remembers the logins and stores cookies. The other deletes all on exit. Its the beat of both worlds.