What's surprising to me is that you're getting that much motivational power out of Beeminder even without pledging money to stay on your yellow brick roads. Theoretically, that's where the real motivational power comes from -- setting up a commitment device.
Well, you'll eventually have some suggestive data one way or the other; my guess, though, is that there won't be a strong correlation between precommitment amounts and success.
Rather, I expect you'll mostly see people who 1) keep running off roads or giving up, or 2) who succeed after a small number of failures. People who crank up to a midrange and then stay on their road(s) forever after seem unlikely to me. (This is why I think private branding or flat-fee approaches are your best bet for stable and sustainable funding in the long term.)
I could be wrong, of course. An awful lot depends on what population you end up being a cross-section of.
I figure by solving akrasia
That's not going to happen, trust me. ;-) There is no silver bullet for that (i.e., no universal solution that doesn't require extensive individual customization), and I've worked with plenty of people for whom Beeminder would be a curse rather than a blessing.
Part of the point is that humans are not homo economicus: not all values are fungible, and some values are in conflict within a given individual.
I'd like to share my specific motivation for writing Can the Chain Still Hold You?
I agree with Yvain that akrasia is probably a major reason that rationality alone doesn't create superheroes. You might be much better than average at making good decisions based on an accurate model of reality, but that doesn't mean you can follow through with them.
Many people report that their thinking is clearer and better as a result of Less Wrong. But despite our many, many attempts to hack away at the problem of akrasia (more: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10), I haven't heard of many LWers conquering akrasia.
But I still have hope that this is possible. In 2006, we finally got a decent psychological theory of procrastination, much better than the old decisional-avoidant-arousal theory. On the timescale of progress in psychology, 2006 is basically yesterday. The first book on how to apply this new theory to daily life was published in late 2010. There is no community of people systematically practicing these techniques and reporting their results.
So it seems to me there is a lot of low-hanging fruit to be scooped up in the field of procrastination research. If we try and test enough things, and especially if our tests our theory-guided, we may be able to learn new things and flip a few causal factors such that the chain of akrasia no longer holds us — at least, not as tightly as before.