Occasionally, I see this, and my instinct is to say, "What an idiot!", but I have to ask anyway. Perhaps there are some valid reasons for this.

You're in a Double or nothing, you have one shortstack player all-in, with two other callers on the bubble. The flop comes out, and someone bets. Why? Does it ever make any sense to bet here?

I could check down a royal flush, because it makes no difference whether I bet or not. If I flop a set, however, and I min-bet, and my opponent is on fairly short stack, but can afford a few calls, maybe it makes some sense, because then if I lose to the all-in player hitting a flush or straight, I would then have more of the other player's chips, making him the new short stack. However, don't I want the other player to hit his flush/straight and therefore win the tournament for me? I really don't want him to fold his suited connectors because there's only one heart on the board. I would want him to hit his backdoor flush, because then I would win too.

So much of this also depends on stack size, etc. When does a bet make sense here? Ever?

I've seen bluffs on the river, that have left me scratching my head. I've also seen big stacks push all-in on the flop. I can't make any sense of those plays...

This is why I don't like the Double or Nothing Sit N Go's. I would say if you had enough chips then don't bet unless you have the nuts and if you are the shortstack you should be willing to gamble more.

Yeah, I think it is a stupid move, though when I play double or Nothing sngs, after I get a stack about 4000 or more, I just sit out and make cash.

And yeah, I don't play these that much anymore

There should never be a bet post flop with two bigger stacks against the all in short stack ever. But people do it at the lower levels all the time. How high are you playing and seeing this?

$5.20's.

The last one that made me completely nuts was a guy with a stack of 6,000+. I had about 2,000. Blinds were at 200/400. Shortstack moves all-in for around 800 in late position. I called with AX suited in small blind, big stack calls with pocket 4's in BB. Flop 4XX, but giving me a flush draw. He goes all-in. I can't possibly call. He eliminated the final player, so I guess it worked out ok, but I was screaming in my head. Prolly a good thing that chat gets turned off.

Yes, I really did see a river bluff in one of these $5.20's. Luckily (for all of us) his King high was still good enough to take down the pot.

Honestly, sometimes I wonder if people don't realize that they're playing a Double Or Nothing.

Regardless, these seem to be getting tougher now. 3 weeks ago, these things were a breeze. I think other players figured out how grindable these were.

Yeah, I played a bunch of them at first and started racking up a good record; then after a week or so it became noticeably tougher and I stopped playing them while I was still ahead in them overall, since I really don't enjoy playing them whatsoever and was only doing it for the "easy" money.

I see this all the time, much to my chagrin.

A big stack may do it, even with no side pot, even with a losing hand, because the short stack on the bubble allows him to continue liberally stealing from the other stacks. Even if the short stack doubles through, the bubble remains and he can continue stealing. With the bubble, average and other short stacks stay tight, not wanting to donk out. This allows the big stack to build a bigger stack and come out of the bubble with an even more commanding lead over the remaining stacks. If the shorty disappears, he loses that edge.

I hate it and personally don't take that approach, but that's the idea.

In a double or nothing, though, it's really dumb, since there's no higher payout to advance to once the bubble bursts. Maybe this guy didn't have the sense to adjust.