A million flies are attracted to shit. I don't believe this sort of training data will ever become useful if it's in the same pool with the rest of the world. See also: voting with your wallet against the tyranny of the majority of uninformed consumers who buy whatever is most marketed. Those pennies don't matter.
In fact, I believe this sort of training and optimization for the mainstream plays a role in allowing bad results to proliferate.
This is before we even consider the fact that clicking on many results can indicate that they're bad (I click another result because the previous wasn't good), or because they're good (I'm browsing choices). Dwelling long can be bad (crappy & slow site, it takes me long to find the information I want or turn away) or it can be good (I found good stuff and I'm spending a while on it). Whatever conclusion your training system draws might be completely wrong. And probably prone to being gamed.