I might be hopelessly behind the curve on this, since I've spent a lot of time seriously disconnected from people... but then, I thought the same thing about PayPal's micropayments and apparently other people missed out on that, too. (Search the forum if you're one of them. There was a post about them a year ago. Or just Google it.)
Does everybody who's doing serials or otherwise frequently-updating sites have an RSS feed, and is everybody putting their feeds on Kindle?
The first time the idea was proposed to me by a reader, I thought it was silly... Amazon would charge them to read my free content? And on a platform that -has- a web browser? Anyway, it sounded like a lot of work. So I didn't look into it at all until much later, and I've learned that it's almost no work at all, it gives the reader a much better experience reading on their Kindle than using the web browser, it's more convenient for people who tend to do their electronic reading on their Kindle anyways, and basically you never say "no" when a reader says "Can I give you money and make it easier for me to keep up with your work all at the same time?"
Getting your work into the Kindle Blogs store is not going to be the gateway to instant fame and fortune. You might occasionally have someone stumble across it by accident but there are a lot of other blogs they could stumble into first. Basically people have to be looking for it to find it. But if you have readers and they have Kindles, this could be worth your while.
(Potential downside: Your feed must have the full story, not a summary or excerpt. If you have pageview-based income, this can cut into it. You can possibly get around this by setting up two feeds, one that you link to on the site and one that you point Kindle towards. But really, while I used to distrust a full-story feed, I think the upsides in terms of making it easy for readers to keep up with you outweigh the downsides that might come from lost pageviews. And there are ways to embed ads in RSS feeds.)
Here's the website. Note that the website only works in IE and Firefox.