Oftentimes I've noticed a lot of formatting issues or misspellings and those will be corrected later. Other than that, I don't think they can edit content without the express permission of the author.
As for the trees - yeah. I LOVE that I've been able to get a bunch of classics and reread them and I have the entire GA Henty book set which are GREAT historical fiction books for teen boys. They are quite expensive so it's nice to get all 95 books for free!!!
But for good reference books, I want them in my hand so I don't have any on my Kindle that I know of. Any that I use are in paper copy.