Keeping Your "Classic" Version - A Necessity?

Launching a site quickly around an idea to claim a first mover advantage is rapidly becoming a mantra for new Web 2.0 startup sites. 

As new social networks and other types social media tools on websites pop up - many are simply exploring an idea quickly to see if it sticks, and aiming to put in more work to redesign or add features at a later stage.  Added to this is the large number of sites that have grown their audiences before the rise of Web2.0 competitors (and the increasingly attempt now to replace the QWERTY keyboard has failed, despite the fact that new designs may be superior in every way. 

Sometimes what people are used to wins despite every logical reason to switch.