We've editorialized about spam in the past, and all the arguments we've made in the past are still true, but every now and then, you get to see the argument presented effectively.
Barry Shein is an old-timer, in terms of the Internet. He was around for the Great Renaming, and was there when most communications was done by modems... 1200 baud modems. So, when he talks about the problems spam causes his business you should listen. The World is a small ISP, and the costs there are high for fighting spam (and, inevitably, those costs are passed on to you!) Can you image what they must be like for AOL, MSN, or the other large ISP's?
Here at DBR, our mail server already blocks email from all of Asia and Latin America; not because we have anything against those areas of the world, but because all we see from those domains is spam. Eventually, I suppose we will lose a piece of real mail from there, and we honestly regret that, but the thought of filtering through the hundreds of spams per day that removing that rule would dump in our mailbox is daunting, to say the least.
In the short term, I guess only filtering at the MTA level will work (once it hits spamassassin or the like, the transport costs have already been incurred by your ISP) and that is a game of whack-a-mole. The long term insists that there be a replacement for sendmail. One option is micropayments, which would end a lot of mailing lists and the like, The other is some form of encryption/trusted system. Finally, there is abandoning SMTP for a new, secure protocol.