as it is not just about selling questionable goods.

It is also a conduit to a) infect your computer via the email, via activex, javascript, buffer overflows from the jpeg exploit, etc.
b) infect your computer with a link to a website in the email, which very well might not be selling anything but of 'interest' to you, and targetted at you.

For example spammers are now targetting c** employees with emails to websites that look legit but infect them.

and they actually can be used as an attack, by sending so much spam it overloads the email server and real email can't get thru.

I had 'bounce' spam once send me 8,000 emails in one day from some chinese spammers address. Wasn't even sent directly to me but the guy had sent out so many spams and faked my domain's email address I got 8000 emails.