I'd be fine with ads in ebooks if the ads were confined to a page [or pages] at the start or end of the book. That is if it meant that a lot of currently unavailable books would become available at reasonable price and at good quality; well formatted and proofed against the original paper book release. To me it would not be worth the trouble to unpack the ebook (talking about ePub format here of course) just to remove the offending pages.