Well, since Ubuntu seems to have more steam than a tea kettle, I'll point this out:

http://lxer.com/module/newswire/view/55975/index.html

Cute.....EVERY USER ON THE SYSTEM CAN SEE EVERY USER NAME AND PASSWORD ON THE SYSTEM... Not that I use Ubuntu, I've installed it and looked at it and decided this no root but you can sudo to anything WITHOUT a passwd wasn't for me so I put Slackware and Free BSDon that box.