This may just be my fat fingers on my phone.
But just in case it's not... have there always been two 'log out' buttons? (one next to FAQ/members and one near the top). I seem to remember reading an old thread about moving it, with the consensus that we never want to log out deliberately so it could be hidden as far from danger of accidental use as possible, or words to that effect.
The last few days, I've kept logging myself out accidentally by hitting the FAQ/members one. Has it appeared recently, or are my fingers getting fatter?!