[anamax]

In other words, you want the USPS to discriminate on something other than cost of delivery.

Why should we enact your preferences instead of, say, mine?

Note that it's quite possible that spam is helping to keep first class postage prices down. (Eliminating 30% of the USPS's revenue does not eliminate 30% of their costs. FWIW, I suspect that direct mail is a greater percentage of their revenue than 30%.)

While you may willing to pay more to send USPS mail in return for getting less spam, other people probably aren't.

Which reminds me - you have gone to the very slight trouble of the first two steps listed at http://www.epa.gov/region1/communities/stop_spam.html , right?