Spam really is a kind of arms race, with spammers trying to develop the most efficient way of annoying people, and email companies and network security staff trying to stop them.
And I really don't understand the point. Does anyone, ever click on all those many thousands of spams? I know once they set up a program, like with snowshoe spamming, they probably don't have to do much to send out to thousands of people, but I still don't see how they could possibly be making enough to justify the effort.
I mean, all they could do is one sale, and if the product is good enough to justify repeat customers, wouldn't they be better off just holding legitimate advertising campaigns?
I'm sure they must make money though, or they wouldn't bother. And I know a lot of spam really exists to insert malicious software onto your computer, so there is that aspect as well.