(Finally found made time to weigh in on this, which is a topic I have active thinkings around.)
I wrestle with the punishment aspect of Beeminder all the time—or, rather, with finding a way to harness it that works for my particular brain. I joined Beeminder in late 2014 and have been more active and less active (to the point of non-active) in fairly predictable cycles:
- I create a spate of sensible goals that I truly want to achieve.
- I spend several weeks to a few months dispatching beemergencies and building buffer to lower the number of beemergencies.
- I start feeling like life is one big scheduling time bomb bearing down on me.
- I archive or flat-road most or all of my goals and go off to regroup.
It isn’t that Beeminder doesn’t work—it works perfectly. It gets my butt going on things I want to do but would never do without Beeminder. It’s just that for my personality, which tends to overdelivery, unnecessary perfectionism, and harshing on myself for failure, the very fact of Beeminder working turns into a heavy burden.
Then I have another set of data, from using a tool called StepBet in 2019. StepBet is a one-trick pony: you can make yourself walk more steps with it, and that’s it. But it’s a great trick, and my experience was radically different than my experience using Beeminder. Let me explain.
In StepBet, you put $40 into a collective pot with umptyhundred other people and promise to make your personal target steps every single day for six weeks. If you miss even one day, your money’s gone. But if you make it, you get your $40 back, plus a cut of the money lost by everyone who didn’t make it. This makes it a combination of positive punishment (do the behavior or you’ll pay money—just as with Beeminder) and positive reinforcement (do the behavior and you’ll be rewarded with extra money).
Turns out that this method makes all the difference in my experience of having to do the thing I said I wanted to do. It is super, super motivating in a way that “do it or you’ll pay” eventually ends up feeling oppressive or suffocating to me. I think there are two aspects to this:
- I’ve already paid the money up front, so it doesn’t feel like punishment; it feels like reward. (This is directly related to your point, @aleix.)
- The prospect of earning a real reward if I stick it out the whole six weeks makes it feel like a game I can win.
There’s a net feeling of having accomplished something that I don’t get from just avoiding paying money at the moment I slip up. In my brain, every StepBet day completed feels like progress (I’m closer to getting $40+ dollars!); every Beeminder day I complete feels like maintaining (still alive, but it’ll probably kill me in the morning ).
Now that I’m thinking out loud: perhaps the presence of a short-term end date is a factor—StepBet always ends in a few weeks, while all my Beeminder goals are forever goals. Perhaps if I set six-week Beeminder goals, the sense of treading water would become a sense of forward progress. Worth more thought! Because I love Beeminder, and have no plan to abandon it ever. But consistently feeling more like I’m gaining altitude and less like I’m putting out fires would be a welcome change. 
 That’s just a Princess Bride reference, for those who are now alarmed at how seriously I’m taking my Beeminder goals…
 The QS aspect of long-term graphs does feel like a reward, though, and I’m already trying to use that to max effect.