This is kind of an interesting discussion, but one of the common things that's been known to happen in the 50s-70s is how certain master tapes (or rather master reels) would be reused as a form of broadcast. As a result, the original program that would be stored on the master copy would be erased, leaving the only other copy that the program can possibly exist is either through a copy that's been given to the TV studio, or if somebody happens to have it recorded off TV.

A lot of the well known British TV shows have been known for wiping. Mainly because networks like BBC have not considered archiving their shows until 1976. The biggest example of that is some of the early Doctor Who episodes. Over 100+ episodes of Doctor Who have been wiped by BBC, and people from all over the world are still out there trying to scout the missing episodes, with up to 41 recovered as of December 2011.

America hasn't been as bad as the UK, since they mostly keep their scripted shows archived. The ones that don't are mainly Soap Operas and shows that aired on the defunct Dumont channel. Though they did wipe a lot of sporting events including the first two Super Bowls.

So, what programs do you know of that have been wiped?

I know of none. Though I would say there are several live events and sporting events that probably have been wiped. That is very interesting for sure. I did not know that about the Doctor Who series.

While I'm familar with the concept, I am not aware of any significant effect it's had on any series I love. There were some "lost episodes" of The Honeymooners, perhaps my favorite series of all time, but as I understand things most have been recovered.

Old game shows, soaps, and some talk shows. I can't think of any particular series off the top of my head though.

Ricki Lake's talk show was wiped, but then came back.

Wow, interesting stuff. Those old reels must have been expensive to warrant a studio to simply record over them. I guess back then with limited technology no one ever thought a episode would need to be recorded twice.