From time to time in Lion I make a test account, a standard account to try things out in. I've noticed the last two times I've deleted the accounts, which no longer show up the System Preferences for Users, that the user folder is still on my drive. When I delete my test users I select a "Erase Home Folder Securely" along with "Delete Home Folder." For some reason it's not deleting the user folder. If I choose any other options to delete the user it works fine. Bug perhaps?