I've got them too and they seem to be the result of domain name registrations.
Here's my sceneario:
I've got one domain name still registered with Network Solutions and 9 with DirectNIC. ALL of the spams go to the NS registered domain name but the user part of the address for each spam is one of the different DirectNIC domain names. A few oddball addresses appear to have been picked up from website pages.
Some of my DirectNic domain names are nothing more than pointers and I've never submitted them anywhere. Unless DirectNic and Network solutions are connected in some way, my guess is someone at ICANN (?) or wherever the registrars deal with have someone feeding info to a ruthless spammer.
Hell, I've recieved phone calls from registration compaines telling me my domain name is about to expire and, if I'd like, they can register it for me
Come to think of it, I have a letter from NetworkSolutions regarding an upcomming expiration for one of my DirectNIC domain names... so apparently they are connected somewheres (or sharing info).
I think my nuts are starting to itch
