As I mentioned two posts ago, Harvard has an unusual tradition of a "shopping period" -- you don't preregister for a class, but you choose classes after the first week, after you've had a chance to go to a lecture or two and see how you like it.
As a student, I loved it. What better way to get an idea if you'll like a class than to go, hear the professor, check out the syllabus, see who else is thinking of taking the class, etc. It makes choosing classes much more flexible. Instead of switching out of classes you've already chosen without seeing, you choose later. Part of that benefit might just be psychological -- most schools allow you to change courses in the first few weeks fairly easily -- but there is a marked difference between changing your classes and choosing your classes, especially if a student has to fill out forms or get signatures to change a class. The openness of the first week is a real benefit to students. I can understand why something like shopping period just might not be feasible for some very large schools, but I think it's a shame more schools don't do it.
Several years ago, there was a movement by the administration to introduce preregistration and get rid of shopping period. I was on the Committee for Undergraduate Education and the Faculty Council, and when the idea was first brought up I spoke against it, only to find that the issue didn't seem up for discussion; it apparently had been "decided" higher up. (It's things like this that helped make the Presidency of Larry Summers so unpopular, as opposed to some of the supposed reasons popularized in the press.) I was surprised that so many faculty on these advisory committees seemed willing to go along with the idea. It was massively unpopular among Computer Science faculty; we like students being able to choose their courses.
Overall, naturally, students didn't seem to like the idea. The administration's main argument seemed to be that it would allow more accurate predictions of class sizes in advance, so Teaching Assistants (and, in some classes, classrooms) could be assigned more readily and efficiently. (Here's an old Crimson opinion giving both sides of the issue.) This was around a time period where there were murmurs of graduate student unionization, and that might have been influencing the administration's mindset. Of course, nobody in the administration had an answer when I asked what prediction mechanisms they were using now, and if there was any evidence that preregistration would help predictions any. (I wasn't the only one asking this question. This was another reason the CS faculty in particular were against the idea; they saw no reason for it. It's in interesting problem to design an enrollment predictor; one semester, Stuart Shieber ended up running a projects class to find solutions for the problem.)
A funny thing happened, though. The change had to be approved by the faculty, and while I seemed to be a lonely voice with objections in these committee meetings, apparently a lot of faculty didn't actually like the idea. Instead of it being a quick and simple vote like the administration seemed to expect, the faculty meeting was a disaster. Eleven faculty spoke on the issue; ten spoke against it (including, I'm happy to say, me). Quietly, pre-registration was dropped as an issue, and shopping period continues.