How can facebook and twitter be used in lectures?

Facebook and twitter seems to be the new trend for this year. People use these types of social networks to communitcate with friends and families, also join groups that they want to be part of. If the university decided to use facebook or twiiter for their lectures, I think it could work. They will be able to give updates on the work that students have to do and also they can interact one on one with the student if they are struggling, with out the lecturer being their. Aslo if a student happens to be ill or is not able to come to the lecture, they could go on twitter or facebook and find the materials for that lecture they missed.