Our new home that we purchased 3 years ago was already pre-wired with Cat5.
A lot of newer home are coming pre-wired already, especially if there is an alarm system already built in.
It's funny, pre-wiring was not even on my radar when we were looking for a house.
Thank goodness it was already or I don't know what I would do now without it.
I've got 2 DirecTV boxes, Xbox, 2 Blu-ray players, desktop PC and 3 WDTV players all connected via Cat5