Hollywood seems to treat digital media like DVD as the greatest threat to their existence ever crafted. But it appears to me that DVD may have saved 24.
From the second season onward, there has been intense pressure on the makers of 24 to convert from their popular serialized format (all 24 episodes are one story arc) to a more usual format where each episode stands on its own. While prior shows like Alias and X-files have had running story arcs, their individual episodes stood on their own much better than do episodes of 24. What that means is that 24 does not syndicate well at all, cutting off a very lucrative revenue stream.
But what makes 24 difficult to syndicate makes it a very popular DVD offering. In fact, if you look on Amazon, all five seasons are among the top 20-30 sellers in the DVD category. Incredibly, a DVD of the first four episodes of the new season, which were televised about a week ago(!), is ranked #16. My guess is that DVD sales do not fully make up for lost syndication revenue (I have no idea of the exact numbers) but these sales must have made it easier to continue down this innovative path.