Help on exit
Most of the online services I use put the "Sign out" link at the end of a drop-down list in the top right corner of the site. This has become a useful convention that allows everyone to just click this link and leave the site without bothering what the rest of the links are about and without giving further explanations. But Facebook thinks that it can violate this convention. So the last link in their drop-down list today is "Help", not "Sign out".