Of course people can do things that are self-defeating - did I ever suggest otherwise? I never said people are perfect guardians of their own self-interest, I said, and I repeat, that a random person is a better guardians of his own self-interest than a random do-gooder.

I am getting a little frustrated with people arguing against strawmans of my positions, which has now happened several times on this thread. Am I being unclear?

None of those links suggest that people are worse guardians of their own self-interest than the outsider. In fact, quite the reverse. Take the fertilizer study. The reason that the farmers weren't following the advice of the Kenyan Ministry of Agriculture was that it was bad advice. To quote:

[T]he full package recommended by the Ministry of Agriculture is highly unprofitable on average for the farmers in our sample... the official recommendations are not adapted to many farmers in the region.

So the study demonstrates that the farmers were better guardians of their own self-interest than some bureaucrat in Nairobi (no doubt advised by a western NGO). If they had been forced to follow the (no doubt well-meaning) advice, they would have been much worse off. Maybe some would have died. Now, at the same time, they don't know every possible combination, and it turns out that if they changed their farming methodology, they could become more productive. Great! That's how society advances - by persuading people as to what is in their self-interest, not by making someone else their guardian.