Last June, Inside Higher Education noted a legal case  against the University of Calgary, filed by two students there who had been punished in various ways for making highly critical comments about a professor whose course they'd taken. Students are of course free to make highly critical comments about professors, and they shouldn't face suspension or lawsuits  for making them.
The Calgary students have now won their case. 
Facebook, Rate My Professors, blogs -- These have become important sources of information about university professors. More important than ever. UD guesses that a combination of new technologies and money worries has made substandard professors increasingly common at some universities. The technologies -- PowerPoint in particular -- make it possible for lazy people to lean on a podium and read bullet points for fifty minutes; the financial worries encourage administrators to staff courses with cheap, unready instructors.
The only way students can fight back, and warn other students to stay away, is through these media.
Free speech is the major, salient, issue here; but the specific, underlying one is just as important: Students should feel free to complain - loudly - about seriously inadequate instructors. Since we can probably expect to see more and more such instructors, all university students need to be assured of legal protection; and of course their outlets for complaint also need to be protected.