Validate email addresses?
If a user adds an email address to their profile, it should probably be checked.
It is important that only one user has a given address (for password reset, and for logging in #157).
It is pretty useless for someone to add someone else's email to their profile (they are just setting themselves up to get it stolen), however it will prevent that person from adding the address to their own account, which would be confusing.
This would require a couple more database fields and a bit of code.