There's also the aspect of social pressure to use the platform. I remember how quickly people stopped using IM and moved their entire online presence to Facebo

There's also the aspect of social pressure to use the platform. I remember how quickly people stopped using IM and moved their entire online presence to Facebook, including the announcement and discussion of planned events. As an IM user who never moved, it kinda sucked. :) I guess you could say the same about the move from ICQ to Windows/MSN Messenger, though.