I've locked the member. A few other people got messages from them as well.
To clarify your other statement about "email address not being safe though" you are wrong. They do not have your email address, and cannot get it off of the site. It is impossible unless they physically hack into the site and access the database. Member email address are displayed no where on the site for someone to just get. Any email sent from the site, to a member, is sent directly from our server. This is why the guy had to sign up to the site, so he could use this messaging feature to send the email.
Don't worry about it any longer though because like I said, no one has your email address, I've locked the member, and I'm going to keep a watch out for suspicious activity in the future.