This short article on R/W Web gives a quick intro on why you should pay attention to early adopters of your product, but also not wait until it’s too late to “cross the chasm” and rake in the mainstream users.
Picture from the Chasm Group.
A common entrepreneur misstep, ignoring early adopters and instead going straight for the mainstream market:
Picture from Tara Hunt
Read the full article, I do no justice summarizing here (on purpose!)