One of my first customizations after installing Mac OS X Lion was to remove the annoying login – username option from the top menu bar. And to explain “annoying”, I find it quite too long displaying my Name Surname, and an option that I would never need to use, as there’s only a single user on my Mac.
Removing it is quite easy: hold command button and drag it off the menu bar.
If you really want to keep it, you can reduce its length to the username or to an icon:
System Preferences -> Users & Groups -> Login Options -> (Click on the bottom left lock if everything is greyed-out) -> Show fast switching user menu as… -> Check/uncheck to show/hide it, or use the drop-down menu for the various options.