Thing #10, Wikis

As I study all these "Web 2.0" technologies, I wonder which of them will become established parts of life (as Wikipedia has become) and which will be quickly forgotten. Which will be time-saving and practical, and which will not be worth the effort? I use Wikipedia as much as the next person (a lot!) for looking up simple information, but I wonder to what extent other wikis will become part of the classroom and the workplace.