Spam from 43Folders?

I have a domain, whenever I sign up for a site I set up my email address to be site@domain-name.com. If I get spam, I check the "to:" field to see which address it is going to and consequently, who it came from.

Today I received a piece of spam today that was addressed to "43folders@domain-name.com". The only place I used that address was here at these boards and at the wiki so it had to come from one of the two.

In my profile I had it set to "Hide your e-mail address but allow form e-mail." so it could have come from there. Does anyone have any idea how else the address could have been spammed?

Thanks!