Well, I don't mind so much that the origin is lost, it becomes a pleasant bit of trivia I will inflict upon my hapless colleagues one day, just as I now explain exactly what the phrase "core dump" really means.
But in this case I do like keeping true to the specific meaning even if the origin is lost in antiquity. I feel it's a useful distinction to make. As an example, I would say that some years ago John Dvorak jumped the shark when he turned his public personal into a troll. As a counter-example, Joel Spolsky didn't jump the shark: He woke up one day and decided that his blog had run its course.
I hope we are able to save some of its distinct meaning until some other phrase comes along with a similar usage.
A few years ago I heard Henry Winkler (who played "the Fonz," for those who don't know) give an interview on some radio show (probably NPR). They asked him about the phrase, and he said what was interesting to him about it was that after the "jump the shark" episode the show began attaining its highest ratings ever.
To me, that's a critical aspect of the term. They are out of ideas, they know it, and they shoot straight for pandering.
People pander for a reason. It works.
There's also a signaling mechanism involved in the use of the term, which is probably part of why everyone leaps so fast to declare that everything has jumped the shark. "I, sophisticated me, have noticed that X is out of ideas and is now just pandering and spinning. You, the plebians, may still tune in for a while, but I in my sophistication have already noticed the downfall beginning." In my opinion, to really know for sure when a shark was jumped takes time. It's like trying to declare five days after an album comes out that people will consider it a classic in 30 years; you really can't do that, or at least you can't actually be sure. The only way to apply the test of time is with time.
I agree with you about signaling, but I thought there might be another effect here. The people that started the term sounded like they watched the show when they were young. It could have simply been that they revisited the show when they were a bit older, and realized "it sucks." Not because the show was very different, but because they were.
I didn't watch the show (although I was/am the right age to have done so), so I don't have an opinion as to whether the show got better, worse, or stayed the same after that episode.
But in this case I do like keeping true to the specific meaning even if the origin is lost in antiquity. I feel it's a useful distinction to make. As an example, I would say that some years ago John Dvorak jumped the shark when he turned his public personal into a troll. As a counter-example, Joel Spolsky didn't jump the shark: He woke up one day and decided that his blog had run its course.
I hope we are able to save some of its distinct meaning until some other phrase comes along with a similar usage.