[jibbed123]

It doesn't feed back into the ML directly, according to Google. Instead they use it to evaluate changes to search algorithms. If they get an increase in thumbs up back from the Quality Raters then their changes were positive. If not, they figure out why.

[tyingq]

The original 2012 FTC investigation of Google anti-trust activity showed how they might have abused this process. Interesting read, no matter which side you take: http://graphics.wsj.com/google-ftc-report/