Interesting. I just found Cory Doctorow expressing a similar view here:

Every time I put a book online for free, I get emails from readers who want to send me donations for the book. I appreciate their generous spirit, but I'm not interested in cash donations, because my publishers are really important to me. They contriebute immeasurably to the book, improving it, introducing it to an audience I could never reach, helping me do more with my work. I have no desire to cut them out of the loop.

In his case, he's apparently set up a system for readers to buy copies and have them donated to libraries.