I've had a few run-ins with that spam attack that is often used against Exp Eng sites which creates endless member accounts for the sole purpose of adding links back to whatever the spammers are trying to promote. The Member's URL in the member profile is used for this.
I'm working on a site that basically locks down everything so that comments and other content are only available to logged in members. Since search engines would not be logged in they wouldn't see any comments and wouldn't see any spam link backs in the comments. Not that this would really dissuade spammers.
I wanted to do the same for Member Profiles so that they can only be seen by other members who are logged in. As far as I know there doesn't seem to be a preference for this. Any ideas on preventing public access to member profile pages?