Most of the spam that slips through to me is coming from a couple of countries that do not have DNS blacklists available on the Blacklists page.
I think I once read in the forum that more country blacklist options were not offered because they wanted a set of blacklist options that could be generally recommended to be turned on.
If that's the case, how about a link on the Blacklists page to a separate "advanced" page, and make other country blacklists available on that separate page?
I'm not suggesting that a blacklist for every country be added--just a few additional countries that are the source of a lot of spam but are not currently available on the Blacklists page. People who didn't want to use the lists (and people who oppose country blacklists on a philosophical or political basis) wouldn't have to use them, but they would help some people.
I could say goodbye to Glut H. Aquifer and Hellenization S. Suarez and their webmail friends forever.