Copyright, TV, and BitTorrent: what is the deal, legally?

I was always under the impression that the downloading of TV shows wasn’t that big of a deal and that no one really cared one way or another. I’m now hearing some tales of networks like NBC sending out cease-and-desist letters for downloading their shows.

Now, I totally agree that downloading movies and music is stealing, but TV? Seriously? If the household has cable, how is it any different than setting a VCR to record, so you can watch shows later?