The case of Ashesi University in Ghana is interesting:
In the Quantitative Methods class, Edward came up with a hashtag that he and Andrew use to curate tweets for the class. “I constantly monitor the class hashtag, and make sure I respond to questions from students as soon as I see them. It is a quick way to help students with problems with their assignments and class projects, and to get involved with them when they’re having study group discussions.” Dr. Larssen however, is encouraging students to tweet during class as well, not just out of class.
For her Software Engineering class for example, members are allowed and encouraged to tweet questions and comments about the class content or the lecture while the class is ongoing. She then addresses the questions either verbally (or on Twitter) or after class. “I encourage the class to tweet their comments and questions using our class hashtag. I’ve noticed that students who otherwise are not too active in class contribute more.” [Italics added].Source.