[Here's] the Catch 22: If an ISP gives the same deliverability to non-Goodmail-certified messages, then who's going to use it? On the other hand, if an ISP gives better deliverability to Goodmail-certified messages than to other messages (much more likely), then they are to some extent misrepresenting the services they sell to their users, since users expect an ISP to make the best effort to deliver all legitimate e-mails, not just the ones from paying senders.
A Moyers on America article provides an analogy in describing Net Neutrality. The analogy is equally applicable to reputation-based email:
For those companies that pay the fee, their content would breeze through the fast-pass lane at the toll bridge, reaching users more quickly; those who don't pay will be stuck in the crowded, slow-moving line, and users will have to wait longer for their content to load.
An email message travels many Internet roads to reach its destination. During its journey, it "stops" at way stations -- many of which are ISPs. Within the inner sanctum of Sender Reputation stakeholders, Goodmail has earned a marketing coup. It is a long way to the finish line (of protocol acceptance); however, Goodmail's marketing coup was picked up by the trade press and perception (positive or negative) can appear to be reality.