"all it takes is for Carlsen to have just one bad day."
No, it takes way, way more than that. That's the point.
I agree with SF. In a 12-game match, it could easily be decided by one bad day/move for Carlsen and Karjakin just has to make a bunch of draws to hold.
I hate the 12-game match system as well as the double round robin candidates, but that reflects the problem funding the world championship cycle more than anything else.
No, the problem with that is that you'd have to also have Karjakin have no bad days, or even average days, really. Karjakin can hardly afford average days against Magnus. So you need Magnus to be playing way below his average, Karjakin to be playing way above his average basically every game, for chances to realistically emerge. Even if Karjakin got a lucky win, which is actually quite hard to get, he'd have to not allow Magnus something similar. If Karjakin can get a lucky win, it's even easier for Magnus to, because he creates many more opportunities for himself.
Even in the highly unlikely event he makes it to a playoff, his chances are very low to win that playoff. At every corner he has to beat the odds. You underestimate just how good Magnus is. Obviously it's possible, but his odds are quite low.
"all it takes is for Carlsen to have just one bad day."
No, it takes way, way more than that. That's the point.
The real question is, how do stupid people get such high chess ratings? Proof that chess ability doesn't correspond with intelligence.
Or it's stupid to assume a counterexample to your assumption couldn't mean your assumption was wrong. I.e., you expect me to be stupid, and thus have a low chess rating, I don't, and the reason for that couldn't possibly be, your assumption was wrong, no, it must mean that somehow you can be an idiot and achieve 2050 USCF. So you're saying that predicting a chess match says more about intelligence than actually being good at chess. Ok.
...Not to mention the fact that having a high chess rating is helpful in answering the thread topic anyway.