I think something should be made illegal: Professors publishing books and making the students buy them.
For your average student who labours all summer to pay for his/her studies, nothing is more annoying than a teacher telling you you need his book for the class. Said book will, of course, cost you a good $100 of your hard-earned money. Which is 10 hours of work.
Here's my beef: it wouldn't be so bad if the book were actually useful for the class, but what really annoys me is that most of the times, it's barely used. Of course, the prof will refer to a few pages from the book, but very rarely does it offer more insight than what the teacher says.
Case in point: Last year, I had a teacher who told us at the beginning of the semester that we needed the book (which he co-authored, and cost around $100, and new edition, please, because the one from 2 yrs ago isn't good enough) because there would be some topics we won't have time to see in class, which could be in the final. Well, guess what? They weren't.
Now, this year, I've another teacher who makes us buy his book. Which is, almost word-to-word, a reiteration of what he says in class. Down to the examples and analogies he gives. But of course, you need the book, because that's where all the stuff is. And, sneaky, sneaky, the cases to read aren't listed on his course plan; they're in the book. Basically, I'm spending $100 to get a transcript of his course. Book which I HAVE to acquire, because it has the benefit of only quoting the important passages of the relevant cases.
So, message to all professors: Stop doing that! It's annoying!