Good replies to James' question.
I'm like most here "never enough time to watch DVD's". I can blame it on sports (DirecTV)

If not for that, I might be close to caught up by now.
From what I read on the Bd, my collection is a lot smaller than most here. Even with that, I have a lot on the shelf that's un-viewed.
Examples of where I'm at with my stuff:
A-Team's been out for 2-3 years? I have all of the sets and just recently finished S4.
Bewitched: Just started S5 with all of the show on the shelf.
Daniel Boone: Thanks to a great friend I have S1-5. Just started S1.
Dick Van Dyke complete series: In the middle of S3
I Dream of Jeannie: Have the complete series. Middle of S3
Looney Tunes Golden Sets: Have all, just started Vol 2
Munsters complete set: Just started S1
Rockford Files: Have all, nearly done with S3
Taxi: Have S1-4. Still viewing S1
That's some of them. I didn't list the ones where I have 3 seasons and viewing Season 1.
As Gary said, I've also reduced my DVD buying over the last year or so. One reason is the decline of classic TV/DVD releases but the other is that I have enough on the shelf for a while.
I like Williams' post about the reason most of us collect these things. There's nothing like having a library of shows to watch whenever we want to watch them. As for current TV? He said it for me. I've been out of touch since the late 90's with series TV shows.
Wayne mentioned another good question, "rewatchability". Nearly all of mine are the kind that I'll most likely watch again someday. There are maybe 2-3 shows where I'll probably sell or give away eventually.