It is too easy to come up with a just so story like this. How would you rephrase it to make it testable?
Here is a counterstory:
Children have a survival need to learn only well-tested knowledge; they cannot afford to waste their precious developmental years believing wrong ideas. Adults, however, have already survived their juvenile years, and so they are presumably more fit. Furthermore, once an adult successfully reproduces, natural selection no longer cares about them; neither senescence nor gullibility affect an adult’s fitness. Therefore, we should expect children to be skeptical and adults to be gullible.
I am looking forward to the API. I am much more likely to continually use Beeminder if it can be automatically updated or, failing that, updated easily from a mobile device. The site is actually OK (not great) to navigate with a phone, but typing updates is not that easy.
Thanks for the hard work. Beeminder looks like a great tool.