The thing about ebook formatting is that many (most?) seem to want to keep it as similar as possible to print book formatting, so that ebooks look like "real" books. I've even seen people scoff at ebooks formatted differently, saying they aren't "professional". I detest that kind of mentality.
As far as readability goes, I'd suggest there are probably differences between reading web pages on a monitor and reading text on smaller displays, particularly when one is LCD and the other is e-ink. Having said that, though, I'm not aware of anyone doing any serious work on readability on e-readers - as far as I can see, Neilsen, for example, has so far mostly focused on usability issues, and not much, yet, on design and readability. He touches on it in an article on
Kindle Content Design, but only in passing.