House of Cards. I loved season 1, but what happened in the first episode of season 2 disappointed me. It wasn't clever, just a shocking and easy fix to a big problem the main character encountered. I thought he'd resolve it more intelligently. Instead, it felt like cheating; as if the writers didn't know how else to get out of the mess created so they chose an absurd path to make it work.
just a little more on the "jump the shark" term. It actually came from a Happy Days episode in which the Fonze jumped a shark tank. It was cited as tipping point of that show from being quality to being camp... I only heard about this last year or so, thought it was interesting.
I think The Simpsons is a classic example of a show that jumped the shark a long time ago
It is not really jump the shark moments but shows I once liked that engaging in a slow death and meander into pits of crap as it limps to an inglorious end often loyal viewers will switch off half way through last series,