There's nobody dragging names in the dirt here if you ask me....As a previous college student, there's nothing wrong with having an opinion about a teacher and naming said teacher. I had a lot of professors at UCF (Florida) that i thought were good and some i thought should have been retired since they were obviously still there due to tenure and spending all their time on research and not teaching. seriously, some classes, i came in and the teacher would hand out homework and say "you have the book, go learn it"...I had one thermodynamics professor that actually told us he did not have office hours and WOULD NOT answer any questions except for during class....Thermodynamics...do you know how difficult that course is? I had to drop and audit that course so i could find a better professor, that had office hours, to learn from the next semester (if i was lucky)...that's NOT teaching.
when it comes to college professors, i think they need to be rated by their students as a performance measure of their work, just like anyone else who has to have performance reviews. I understand that the money is in the research, but students are paying for a service that's supposed to be provided. College is a LOT of $$$$ nowadays and performance reviews by the students shouldn't be overlooked. If they are and the students don't feel they're getting their full worth, well then yea, you're going to see some backlash by students telling other students to avoid said teacher. Students are paying for a product AND a service. It's up to them to get the result product, it's up to the university and it's staff to provide the service.
If someone wants to steer other students away from particular teachers, I don't see a problem with it as long as there's a stated opinion behind it and it's not considered spamming strictly on a "don't take a class with this professor" thread type thing.