AOL and Yahoo! are implementing a new system which will guarantee a free ride past their spam filters for senders who pay something in the neighborhood of a penny for each email they send. As long as they don't alter their spam filters in ways that generate more false positives to try to force people to buy into the system, I don't have a problem with that. The danger is that they'll try to use the existence of the system to justify a worse false positive rate.
The internet has been a tremendous boon to business--especially small businesses (like mine). Consider the singles site that my brother and I created--we are able to let customers send email to each other through the system without worrying about whether providing that service will break the bank because it doesn't costs us anything extra to allow it. Even customers with free guest accounts can send messages. If we had to pay even a penny per email, the customer would lose, we'd certainly not be able to send email for guest members, and may even have to charge paying customers based on how many messages they send.
Another example--one of the most valuable assets of many online businesses is their email list. Some businesses have lists with thousands or hundreds of thousands of people who have opted in to receive emails from them. You've probably seen the "autoresponder" systems where you sign up to receive a free 30 day email course on some topic or other. You get some useful information for free, and the publisher gets the chance to try for 30 days to sell you on some related product or service. After the course is over, you stay on their list and get occasional related messages until you unsubscrive. If email cost a penny a piece to send, how many small businesses do you think would decide not to try out this valuable method of communication? If you can send a message to your list for nothing, it's a no brainer. If it costs you $500, you've got to be certain your going to net more than $500 per message.
Another example--let's say you've got an online business and a big customer email list. One day, you realize there's something that would be really good for your customers to know--lets say you discover that a part on your product breaks more easily when it's stored on its side. It's not dangerous, and you never claimed that it wouldn't, so you wouldn't be liable for repairs, but your an honest businessperson and you want the customer to know. If notifying your customers is free, again, it's a no brainer. But what if it costs you $500? You might be tempted to keep your mouth shut. How'd you like to be one of your customers in such a situation?
Another example--I'm a participant in the affiliate program of a company that gives me the option to receive an email notification every time someone I referred to them buys. What do you think the chances are of them keeping that benefit if each email they sent cost them money? Maybe they would--a penny an email is small in comparison to the commissions they pay. But on the other hand, it's not a critical service to me, so I wouldn't get all huffy and leave the program if they dropped it, so what incentive do they have to keep it?
Keeping email virtually free is a big win for businesses and customers alike. Allowing customers to pay to get past SPAM filters is a fine idea, as long as those who can't or don't want to pay aren't blocked too aggressively.