Various people in various fora have accused Goodmail Systems of attempting to extort payments out of senders, saying "That's a nice little email you've got there. You wouldn't want it to get hurt, would you?" That's not how it works; not at all.
Traditionally, a protection racket is a subset of extortion. The nominal protector is actually the one who would create the harm in absence of a payment. The exortionist threatens to harm the property owner or his property in exchange for a payment. Of course, this only works if there is no other threat to the property; e.g. another extortionist. Typically, though, the extortionist has eliminated any other extortionists, otherwise the payment would quickly go to zero.
So, first, Goodmail doesn't have a monopoly. Sure, they have first-mover status, but there's no reason why they couldn't be out-competed in the marketplace of email certification. Second of all, Goodmail doesn't own the resources used to create and maintain the mailbox. So if they were the extortionist, then the mailbox provider would be complicit in the extortion. In this view, the sender is the victim, and the provider and Goodmail are acting in concert as the extortionist.
The problem with this view is that folks like AOL and Yahoo have never needed Goodmail to extract payments. They have always had the ability to take a sender aside and say "That's a nice little email you've got there. You wouldn't want it to get hurt, would you?" Yet they have never done this. It's not likely that they would do it now, now that they have a third party (Goodmail Systems) to share any payments with.