Hi Roger,
Once you get on these email list, it's almost impossible to get off. I get 20 - 30 emails a day purporting to come from myself.... >:(
If you do try to blacklist the spam, you just end up locking lock the good emails to. :-\
In my own opinion, there is no "mileage" or money to be made in shutting down the spammers, so why should they bother.
From the reports I glanced through about the big ISP's setting up an authenticating system for emailing, there was almost a fist fight!