Wow

90% is a scarily high figure. Think of the processor power, bandwidth, electricity and ultimately money that's being wasted by ISPs filtering this crap. I'm amazed they haven't come up with something to stop this yet (or at least decided to really go for SPF and/or SenderID), they've spent enough years naval-gazing about it.

Then again, I wonder how much total traffic does mail account for? Perhaps saving 90% of sod-all isn't worth the bother.