A similar trend was observed with Myspace and Facebook. Myspace was doing well all the way up to early 2008, 4 years after the creation of Facebook, which was already becoming quite popular, but then in late 2008 Myspace suddenly became worthless.
A similar 4 year lag time is observed with the iPhone and the sudden decline of Research and Motion.
In both of those cases a switch of sorts was suddenly flipped.