vBulletin User Registration Rules

[Marco van Herwaarden]

1. From a security P.O.V. it is very bad to have the same password as the username. But i don't think this should be a problem, as you are only talking about new registrations.
2. Again, as you only talk about new registrations, this should not be a problem.
3. Again, no problem for new registrations. Also using the same email address multiple times could cause problems (like password recovery, for which account the password should be mailed if the email is not unique). But this can be turned off at:

AdminCP -> vBulletin Options -> User Registration Options -> Require Unique Email Addresses: No