This is an older Galleycat post, but it's one I find pretty interesting. Textbooks are so expensive these days (I've had students mention they paid more than $200 for thick biology and chemistry tomes), but there are still ways to help students out. One of those is to package course materials through campus printing outfits. I've done this before with handouts, essays and writing theory that I've generated for the course. The students pay a nominal fee and end up with a spiral-bound collection of materials.
I used to use a bloated text (Steps to Writing Well) that was strong on theory but was filled with what were, for my tastes, antiquated and dull essays. I went to Bedford/St. Martin's and reviewed their essay/story banks for quality content. I was impressed, so I compiled readers for both my composition and literature sections. I teach the course theory from my own notes and PowerPoints, and I'm able to teach stories and essays I'm passionate about and that I know well.
Because I'm listed as the editor on the front of the text, students invariably assume that I'm enriching myself somehow through using these texts (they both cost the students less than $20.00, by the way).
Of course, I don't see one thin dime from their use.
So, is assigning personal texts a bad idea? Not in my view. So much of higher education is steeped in esoteric knowledge, and many of my colleagues are specialists in their fields. A great many of them have also proved to be excellent writers. I don't see it as a conflict of interest if a professor can use a particularly clear text that he or she has written that sheds light on an area of personal expertise.
Of course, it's a case-by-case deal, and the price and utlitity of the text in question should be thoroughly assessed prior to adding it to the adoption sheet...