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!