It’s really funny to see how popular things can get, and then totally disappear. Some time ago, there was a TV show on the french TV called “Un an de +”, that talked about what was in the news one year before. It was really interesting to see how quickly everybody can forget stuff that looks so important now.
For example, who remembers Second Life? Apparently, it has been on the decline for some time already, according to Google Trends:
Will Facebook be the next Second Life?