Fiber optic networks are slowly taking root in the US, with Verizon's FiOS and AT&T's U-Verse providing internet, phone, and HDTV over fiber to the home. The U-Verse system has only rolled out in San Antonio, Texas so far, but some customers have already figured out how to extend the system.
It seems when AT&T offers multi-room packages, they only provide one DVR, but they will give you additional (identical) boxes with the DVR functionality removed. It only took a couple weeks before someone popped open the back of a unit to see the internal differences between the DVR and the set-top-box w/o DVR.
Turns out they simply unplugged the hard drive sitting in the case, and you can quickly and easily plug it in to gain additonal DVRs on your home system. It's so simple it's almost comical that AT&T did this. [thanks frank!]