> If anything this is the least dubious way to acquire training material.

Yeah, I emotionally felt a little upset because books are being destroyed and I don't like that. But rationally, this seems very much like a win-win.

The second hand bookstores are getting revenue that they otherwise wouldn't be which means they have an easier time staying in business. AI companies get their materials legally. And it possibly pushes a second publishing run which ultimately benefits authors.

I think the only way this is possibly "bad" is if a rare/hard to get book is destroyed from these ventures. That would be horrible. But I doubt that's very likely as there's almost no such thing as a rare book that AI trainers would be particularly interested in.