Target The Forward Fringe:

But when Apple announced the Retina MacBook Pro at WWDC, revamping all of my apps and my web site jumped to the top of my list of priorities…

Why? Because HiDPI customers may be a fringe group, but they are a forward-facing fringe. They represent the users of the future, and the more we cater to them now, the more deeply embedded our products and designs will be in their culture. The future culture.