This reminds me of another astute warning from @lanthala, quoted with permission:
I don’t think Beeminder is harmful, but I do think there are a number of people (percentage unknown) who would do themselves some amount of short-term harm with Beeminder, by doing all the things they think they should do and burning out. Beeminder is the motivational equivalent of steroids for someone who desperately wants to build muscle, and can be abused just as easily by people who haven’t (yet) learned they have limits, and not all of life can be judged by productivity.
That being said, I think those people already have sticks they can beat themself with, and I definitely don’t think things that can harm some people and help others should be removed, so I’m still very pro-Beeminder. But just as I don’t tell certain of my friends about credit card churning, there are also certain of my friends I don’t tell about Beeminder.