Yeah, but it's also the easiest to convert. It's much more difficult to convert from an ebook format to a TXT or RTF file, or from one ebook format to another.

I've had to toss a few ebooks that people have uploaded because they went from an ebook format to TXT, and the formatting and the text was so messed up and garbled, you couldn't read it, and it was clear there was a lot missing from the text in various places.