This was supposed to go in the last post, but it got too long and - fine, you caught me. I forgot - I forgot all about it. It was supposed to be in but I didn't remember. Happy?
High concept - a storytelling feature perfectly suited to RPGs - can act against Things Get Worse. High concept is what you get if you ask a student of the geekly arts for a story that's never been seen before. Literary crossovers, supernatural creatures in mundane lines of work, and groups of people with superpowers that don't lend themselves to dressing up and fighting crime - these are some basic 'formulas' for high concept, but as one might suspect, it's hard to nail down. A brief and arbitrary list of examples in fiction would be Chew (heretofore unexplored superpower) The Five Fists of Science (historical figures in fantastic situations - impossible to describe without giving a full plot summary), and everything Tim Schaeffer has ever done.
For lazy or poor writers, or for those too blinded by the power of the concept, high concept can be a crutch, or even a liability. In the drive to show off the concept, stuff like characterization, plotting, and pacing can be left behind. As can Things Get Worse. If you start with a crazy concept, it's hard to get either the build or twist necessary to keep the story punchy. If your concept is good enough, you can sometimes power through, but that shouldn't be something to plan for.
One great example of TGW versus high concept can be seen in My Favourite Thing on the Internet, MS Paint Adventures. This is a webcomic written like a text-based adventure game, where the transitions between panels are written commands to the characters. He has two stories worth talking about: Problem Sleuth (completed) and Homestuck (ongoing). Problem Sleuth leans on its concept pretty hard. Things still Get Worse, but through build, rather than twist. It doesn't subvert your expectations, save your expectations that one person could come up with all this cosmic, world-shattering raw creativity. It stays fully within the domain of its concept - The Adventure Game that Could Never Be.
Homestuck by contrast, is constantly taking your expectations and hurling them through brick walls. Aside from the more superficial additions, like characters with personalities, actual dialogue, and shiny Flash animations with music, Homestuck asserts its superiority to Problem Sleuth (which, don't get me wrong, is still amazing) even more by having everything go wrong. It retains a concept at least as high as PS's - a group of children in a world governed by video game logic play a game that can affect the realities of their fellow players. Them going through the game, building each other's houses and levelling up their skills and gear would have been interesting, but the repeated instances of everything going completely off the rails turns it from a neat and well-done little comic to a badass epic.
Comparing GMs to authors is always a dangerous analogy, as players of course have input into how the story of a game session develops. Also, players can tend to be cautious when threats to their beloved PCs might arise. Even so, GMs out there, plan to drop a little something unexpected - a new type of challenge, a shift in objectives, a conflict of interest - before the climax of your adventures. Done right, everyone has a better time.