Say you bought a Kindle. If you were to search for Gizmodo in Amazon's Kindle RSS store, you'd notice we're not there. That's not because we don't like it (although I'm not saying we do like it, either). The reasons are strictly business related, which Gaby Darbyshire, Gizmodo's business dev smart person, explained to me in brief.
One main point is that if Amazon was sued for something we wrote, even by some nut job figuring Amazon would settle quickly, we'd have to take the blame. (I make no guarantees to SFW content, per our usual programming.) The bigger issue is that you can still read Gizmodo using Kindle's browser for $0. And you guys are too smart to pay $2 for something you can get for free a few clicks away on the same device. I don't think the RSS store is useless, but I think the business model needs a bit of tweaking. And of course, if it ever makes sense for Gizmodo to be on the RSS feeder and we make it happen, I'll let you know right away.
UPDATE: Ryan Block of Engadget has voiced similar sentiments on his personal blog.