As a student I spent most lectures taking feverish notes in almost illegible handwriting, trying to create a record of what the teacher had said. If you couldn't go to a particular lecture you could ask a friend for a copy of his/her notes (often even more illegible). Some desperate characters were even prepared to pay for a whole term of lecture notes since they had spent most class time elsewhere. Lecture notes, however, are of course totally subjective and there's no guarantee that the note-taker was listening attentively all the time. Their value to anyone else but myself is probably very low.
An article in Inside Higher Ed (Taking notes beyond the classroom) discusses the current growth in lecture note-sharing services on the net. There are now several sites that allow students to share lecture notes and create networks around them - for example GradeGuru and ShareNotes. Students can upload their notes that are then assessed according to popularity and recommendation from fellow students. The sites even pay students if their notes get good reviews from users.
I can see potential in this type of service if it results in students collaborating to produce more than just notes. If a class can collaborate to write "meta-notes" and then build on them by reflecting on and drawing conclusions from what was said in the lecture, the process of comparing lecture notes could lead to a deeper understanding of the subject. This type of collaborative learning can take place using a number of tools such as discussion forums, wikis and various social networks. Start with your rough lecture notes and build on them.
However, if the notes are only used as raw material for cramming before an exam I am less enthusiastic. A simple record of what was said in a lecture does not of course constitute learning and these note-taking sites tend to confirm the myth that passing exams is still all about memorizing what the professor said. With so many lectures being recorded and distributed on the net via iTunes or YouTube, I'm surprised the note-taking sites do so much business. Now you can replay the important parts as often as you like and have access to hundreds of other lectures on the same subject from other universities. Just reading through your (or someone else's) lecture notes will not get you far, it's what you do with them that counts.