$1 email
computers and people excel at different things. it's very easy for a person to tell the difference between legitimate email and spam. it's very difficult for a computer. my brilliant idea is for people to filter spam. if you send me spam i get to charge you $1. there are no technical barriers to creating such a system. the resistance is that people might have to actually freaking pay for emails they send. gah! the horror. one weakness is that sometimes legitimate accounts will be compromised. eg i could steal your password. and then i can send emails from your account. at least until you run out of credit with your mail server. then they cut you off. how many would that be? 100 or so? sure beats the millions of spams that a compromised bot sends out in a day. you'd be inconvenienced. most likely you can call your mail provider and plead theft. they chastise you into securing your system better. maybe they keep your money. remember they already paid the people you sent spam to. maybe they split the difference with you. either way. you learn very quickly to cover your assets.