[Siemer]

"Pulling a MySpace" means messing up your product so badly that your users abandon ship. "Jumping the Shark" means taking your story to such incredible heights that it becomes unbelievable. Not the same thing.

[sethammons]

https://en.m.wikipedia.org/wiki/Jumping_the_shark

Nothing to do with being believable. More to do with being gimmicky and irrelevant.