Yes, but unless these experiments are done by pairs or groups, you are getting what is passed off as scientific results from someone who is experimenting on their own brain with a sample size of one and no control group. How do you trust the results from an experiment conducted on the experimenter's brain? What if the experimenter loses the capacity to properly conduct the experiment in the process? How would you know the difference between that and he or she being incompetent in the first place, aside from the fact that they're attempting this in the first place?

Check out Erowid[1] and see how people dealt with those 'scary chemicals'. People were being their own chemist & pharmacy at much higher doses, for much longer periods than any doctor had ever prescribed. There are certainly uncertainties, but enough people saying similar things actually do start to hone in on very real affects (that aren't/can't actually be known from an 'ethical' experiment).

[1] https://www.erowid.org/

A lot of great discoveries started from anecdotes.

(Or put in in another way: why don't we measure if the number of deers in Germany hair correlates with weather in Australia? Because they are even no anecdotes it does, or wild guesses why it might.)

Sure, a lot of self-reported self-tinkering may be qualified more like high-risk fun. Yet, people performing experiments on their own is not a new story.

The problem is that no one gets any decent data out of that harm. The benefit is pretty minimal compared to the societal cost of potential harm. We can even ignore the personal costs completely and just focus on the societal costs of these people harming themselves and no longer being productive and instead being a burden, it still seems like a poor trade-off.

So, if you are going to self-experiment, please take copious, detailed and careful notes, video and pictures I guess.

It's also very worthwhile to note that groups of well educated, titled experts do horrible things now and then. Take the lobotomy for example, which won it's inventor (Dr. Egas Moniz) the Nobel Peace Prize. It's still around, and has it's place as an incredibly extreme measure, but it was horribly overused at first.

http://motherboard.vice.com/read/a-history-of-the-lobotomy

The same argument goes for electroshock therapy, forced sterilization of 'mongoloids',

http://www.mcgilldaily.com/2014/03/the-science-of-harm/

and a whole bunch of stuff done in World War II. How about lead based paint?

Learning is filled with mistakes but 'Trust us, leave these things to professionals. You could really hurt yourself.' isn't an answer.

What people do with their own brains, ultimately is their own responsibility.

An opportunity which comes blind, and with your brain as the stakes strikes me as something more akin to "A Gamble". It might actually be an incredibly poor gamble too.

It's a gamble for those doing it. If you're willing to let them (and I don't see sufficient grounds on which to stop them) then it's pure upside for everyone else, as we learn the results. Very callously speaking, of course. And the upsides are much less when they're not thoroughly and scientifically recording their results, which they're probably not.

The thing is, you're assuming that the methodology employed by people acting as their own guinea pigs will yield useful data. I think this will be a case of GIGO, and the answers we need will eventually come from study, not personal sacrifice.

Curious why you choose extreme sports as your example.

I know that a lot more people die at the easy end of the spectrum when kayaking. The ones who do it at the extreme level know what they are doing are usually very aware of their own ability.