There's been the usual buzz this year about replacing your notebook with a wiki for taking notes in class. Frankly, the buzz is bullshit. Wikis will never catch on as notebook replacements for a couple of reasons_
1) Mathematical symbols are a pain in the ass to represent in wikis. By the time you get the appropriate symbols and formatting in, you're three equations behind the professor.
2) Assuming you don't have a fancy-pants tablet PC, there's no way to copy diagrams off of the board. I suppose you could use a digicam or something if you were really dedicated, but syncing all the pictures up with the appropriate pages of the wiki would be a pain.
3) Formatting is a pain in the ass to do in a wiki. When I'm taking notes, and there's a REALLY important point, I might write it larger, underline it three times, or put a big star next to it. How do I do that quickly in a wiki? How do I connect concepts with an arrow, or write notes in the margins?
In my experience, wikis and other electronic note-taking tools have far too many disadvantages to make them viable alternatives to paper and a pencil. Sure, having a searchable archive of all my collegiate notes sounds great in principle, but ask yourself_ How often do students really reference their notes from years ago, or even from the previous semester? (hint: it's pretty close to never)
Wikis are great for doing some things, but note taking is not one of them.