I tried to create an account on my site for a friend, but I got a warning:

user warning: Duplicate entry '1' for key 1 query: INSERT INTO users (name, mail, pass, status, init, uid, created, access) VALUES
in /home/sites/drupal/www/master/includes/database.mysql.inc on line 172

Doesn't look like the account was created, even though the web page implied it was.