Here's a bit of good news someone passed onto me yesterday: Researchers who get funding for their surveys from the Russell Sage Foundation are now required to pay crowd workers a fair wage.
"Fair Payment Policy for Crowdsourcing Workers
With increasing frequency, academic researchers use crowdsourcing workers (e.g. MTurk) to complete study-related tasks. RSF requires that compensation for crowdsourcing workers be appropriate for the time and effort that they devote to their study-related task. The payment amount must be based on the minimum wage in the state where the fiscal agent for the award is located or at least $10.00, whichever is higher."
http://www.russellsage.org/how-to-apply/apply-project-awards/budget