The first thing that tracked my attention after upgrading to OS X 10.7 Lion is that my full name (logged in user) was displayed on the top menu bar! Except that I do not want my surname showing up there, I am the only user on my mac. It is very easy to remove this option. You just have to click on the username in the menu bar while holding the Command(?) key and drag it off of the bar.
You can reenable it again, by going into System Preferences > Users & Groups > Login Options and checking the “Show fast user switching menu as” option. If the options are greyed out (and you are not able to modify them), just click the Lock icon at the bottom left corner, typer your password and you are ready to go.