I dont know how but i got this situation:
It shows my facebook name, My account, but no Logout button.
thought it could be important for the beta.
EDIT: I know, that i did not login through facebook to q2a today but through normal login, and I used facebook individually today, I am logged out there but still have this situation. Now I try to login through facebook button to q2a and then log out.
EDIT2 : Now I logged in to q2a using the button, and then the facebook logout button shows up correctly. Logout as well works correctly.
I hope this helps to find the reason for this behaviour.