That's one big mistake. Before anybody will easily send you e-mail he has to get your address from somewhere and determine somehow that the person is interested in hearing from you. That process can just as well include obtaining personal or community authorization.
My address is printed in about two million copies of books that I've written because I want my readers, most of whom are not technically sophisticated, to write to me. That's an extreme case, but lots of people put their e-mail addresses on their business cards and in their newspaper ads because they view e-mail as a way to contact people, not as a way to throw up walls. Much though we wish it were otherwise, spammers can read as well as anyone else and can use those addresses the same as legitimate users. If you put up technical blocks against spammers, you also put up blocks against lots and lots of legitimate e-mail users.
The lack of freedom of press for those who don't own the press also was a social problem. As well as lack of clean water.
Are you're going to tell that political methods solved those problems? To solve them the societies needed the technology first.
They needed both. (I can tell you a fair amount about clean water, being a municipal water commissioner*.) But that doesn't have much to do with spam other than that there are economic externalities in spamming that technical approaches are unlikely to change anytime soon. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Information Superhighwayman wanna-be, http://iecc.com/johnl, Sewer Commissioner Finger for PGP key, f'print = 3A 5B D0 3F D9 A0 6A A4 2D AC 1E 9E A6 36 A3 47 * - Yes, my signature says Sewer Commissioner. It's a small town, I do both.