As of this evening, new measures have been implemented to help ensure a situation like this does not occur. There are now restrictions in place before a new member is given permissions to send private messages.
As I'm sure most of you can imagine, especially if you just look in the average email account, spam is everywhere and people do everything they can to push this garbage out to as many people as possible. Unfortunately, this time they found a temporarily effective way of doing it.
We are sorry for the situation and will, as always, continue to try to prevent this stuff from happening.