Bill Gates foresees a virtually spam-free world in 2006. "Two years from now, spam will be solved," he said at the World Economic Forum in Davos, Switzerland.
Microsoft (along with many other companies) is working on several approaches, including challenge-and-response techniques and computational barriers that would be prohibitive for mass e-mailers. Gates thinks the most promising solution is a kind of a postage you could charge to accept messages from senders who are not on your white list.
I'm not sure exactly how that would work–in particular, how the payments would be processed and transferred–and I don't know how plausible Gates' prediction is. But it would be instructive to knee-jerk regulators if technology could solve the spam problem that quickly.
Already anti-spam software has improved my personal e-mail situation a great deal, but it still takes time to download all those messages prior to sorting (especially if I'm using dial-up), and the network capacity problem can't be addressed with filters on the final recipient's end. It's pretty clear the key to cutting down on total spam traffic is raising the cost of mass mailings; the question is how and how soon.