Blockchains have clearance rates that are a few dozen orders of magnitude too slow for this. Bitcoin for example clears 7 transactions per second.
Famously, the British found x was "fewer cobras" and y was "cobra tails", the opposite of x being "the locals bred cobras to get money for cobra tails".
Make a citizen science weather station that's free, it's all fine. Make it paid, someone's going to grab satellite pics and generate from them plausible but not necessarily accurate simulated weather station data for everywhere to get that money.
Trying to do this with humans on a big scale combines the worst of software development in the days of punched cards, working without anyone having given you a formal language spec, and black-hat hackers on the modern internet.
It is very very easy to pick your incentives badly; you only get feedback on a very slow cycle (in the punched card days you might run the program overnight and only find it crashed on line 32 from a typo the next morning, but it's much slower than that in meatspace); and you also need constant fine-tuning as people interested in gaming the system share their methods for doing so.
It doesn’t work as well as they wanted and it has been subject to various exploits over the years from people figuring out how to fake the participation to extract rewards.
>>Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electronic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model. Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increases transaction costs, limiting the minimum practical transaction size and cutting off the possibility for small casual transactions
From the bitcoin white paper.
>I’m referring to projects like the Helium network, which rewards people for running network nodes
OK, what's the clearance rate for helium?
Visa clears 35,000 a second.
It's the same thing with ad networks, most of the effort goes into verifying that an ad click was legitimate and not a bot. Or that classic story of when the British government tried to eliminate Cobras in India by paying a bounty for every dead cobra, which just led to people breeding more cobras.