I'm confident that there will always be ad-free ereaders. After all, one of their many appeals is a distraction free reading environment.

There is also the question of how much value the companies derive from the ads themselves. Advertising was probably quite valuable when the readers cost over $300 -- the buyers were people with deep pockets and likely represented a smaller and easier to target demographic. But these ads are being used to push ereaders under $100.

I also wonder how many people would end up buying these SO devices and using hacked firmware if ad-infected devices became the only option. After all, the Kobo is fairly open (so much so that I wonder why so few people are hacking it). And while I can't speak for the latest Kindle, there was replacement software for the Kindle.