Steve, a smart guy about Web 2.0 but not as marinated in e-mail best practices as most legitimate marketers and publishers, recommends not only converting all your subs into feeds, but also urges newsletter publishers to use the service to generate feeds from their newsletters.
This totally misses the best practices boat.
Double confirmed opt-in is the e-mail subscription gold standard (and what ClickZ practices, btw). Subscribers must first reply to an e-mail confirming they're intentionally subscribing to the publication before they'll receive it. MailFeed.org cannot accomodate this method.
And besides, most publishers concerned enough about honoring their subscribers' intentions already offer them the option of reading feeds.
Publications such as the one Steve cites in his post (and many others, unfortunately) sign hapless subscribers up for all sorts of stuff they didn't subscribe to, once they have that e-mail address. MailFeed would convert all this e-mail to feeds, sure. But at what cost?
I love the concept, but MailFeed in its current incarnation won't work for teh white-hat mailers. Instead, it would swap out your e-mail spam problem for an RSS spam problem.