Ok, so I'm a little behind on my blog reading..
This article caught my eye a short while ago; Alun is a regular commentator in my blogs, and invariably has something interesting to say:
AOL, Yahoo introduce "pay to spam" service (5 February 2006)
I agree with Alun's opinions on AOL and Yahoo's idea - but one thing does occur to me. About four years ago I walked in to a new job, only to discover that the mail server (they were running Novell and GroupWise) was set as an open relay - so much crap was being pumped through that server (the spammers were smart enough to send their wares outside of business hours), and the NDR load was so great, that the poor server was being brought to its knees every night. This server was being actively cared for by an IT outsourcer... damned if I know why they didn't spot what the hell was going on.
At the sort of volume I saw on that poor server, paying AOL and Yahoo could get expensive very quickly.
The last time I looked into this sort of thing, popular opinion was that around 90% of all spam was being sent out via compromised home PCs... Mum and Dad or Grandma and Grandad's PC with a broadband internet connection and no firewall, or firewall neutralised by malware infection. The heavy duty spammers who use open mail relays and compromised home PCs won't bother paying AOL and Yahoo 1/4 or 1 cent per mail when they can pump the stuff out for free.