A publisher for an e-textbook is offering me an honorarium if I try it with a class. My own ethical take on this is that I would not entertain this regardless of the size of the honorarium (which I don't know). I certainly wouldn't do this without full disclosure to the students who I'm forcing to buy the book. I also don't see this as a particularly good text for my course.
While my own position is sort of steadfast, it's something that I haven't seen before in academic publishing, so I'll ask "Are there situations where taking an honorarium for trying a textbook on a class is acceptable behavior?"