Not necessarily. Why is spam so abundant? Because it costs almost nothing to send. What if, rather than imposing all kinds of laws, we simply imposed a postage fee on e-mail? For example, it would cost $.05 to send a message and nothing to receive it. How many e-mails does the average person send in a week? I'm probably not average, because I don't send a lot of e-mail, but I'll bet that few people send more than 10 e-mails per day. The ISP could allow each user to send mail at no charge to a user supplied list of people. This would lower the cost considerably. It would be easy to add names to the list. If the user begins to send mail to an unfamiliar address, the program could ask him if he wants to add the address to his list of free addresses, and even if he never plans to write them again, he could add it. There would also have to be safeguards to prevent spammers from illegally using someone else's account to send spam.
Because it isn't really "simple." Who collects this? How does any server transporting it know the postage has been paid? Remember, you're not dealing with honest people here. These aren't guys with Earthlink accounts. Most of 'em aren't even in the U.S.