While I don't think anyone should be working all day for less than minimum wage, I wonder who wins if we successfully push back against sites like Mechanical Turk. It's not like Uber, where an actual job that paid a living wage is being replaced with a gig job that pays basically nothing. No amount of lawsuits or lobbying is going to make Mechanical Turk give its workers minimum wage and paid bathroom breaks, it's just going to cause the site to shut down, and instead of getting paid $30 a day, all of the workers are going to make nothing and all the bad things they they needed that $30 to avoid are going to happen.
I think the bigger problem here is the economic circumstances that force people to work for these sites, rather than the sites themselves. If you work retail and they only give you 20-30 hours per week because they don't want to pay you benefits, but they also require you to be available at any time, you can't take a second job, so you're forced to do more flexible work such as filling out surveys on the internet, just to make any extra money, no matter how little it is. If you don't have any job at all, you'll spend 16 hours a day filling out internet surveys, just so you don't starve. The longer hours that someone works these jobs just shows exactly how desperate they are, but that desperation isn't cured by getting rid of their only meager source of income, it's cured by creating an economic safety net that actually works.