In the upper right panel there is by default a drop down menu where you can set your online status, interact with Ubuntu One, etc. It is placed right next to the drop down menu which lets you logout, reboot, shutdown etc.
For me personally I have no use for the online status menu, so I usually remove it. The problem is that it seems to belong to the same panel applet as the actually wanted logout menu, since that menu too disappears. I believe we are talking about the "Indicator Applet Session".
Is there some way I can hide or disable the online status menu, but still keep the neighboring logout menu?
I am running Ubuntu 10.04.
Open the "Ubuntu Software Center" (under the Applications menu). Search for "indicator-me" and remove it. Log out and back in to see the change.
This will remove it for all users on your system. I don't believe there's a way to merely hide it for yourself.