While $2/hr sounds low for the US, this seems viable in countries with super low cost of living. I suspect language barriers are holding back more people from taking advantage of this opportunity.
That sounds like too much, $2 an hour median is more than a median wage in a ton of medium-developed or even quasi-developed countries (say it is under $3 in Russia and just over $2 in Belarus). Jobs on Mechanical Turk are simple and nearly everyone mentally healthy can do it. I wonder why wasn't rate driven much down by people from very poor 3rd world.