I don't the situation is analogous. Amazon would be similar to Uber if they set the price for hit tasks. But they don't the hit submitters can set their prices and there is a vibrant market driving to certain price levels. If Uber let drivers set their own prices in some manner, then Uber would be operating a market. Instead they don't operate a market, they operate a direct to consumer service. I'm not certain if their drivers should be considered contractors or employees, but neither situation would be exposed directly to the consumer unless they switched to a market model.