They were using Mechanical Turk to evaluate existing OCR systems before they started at building their own. If you read further into the article, they did exac

They were using Mechanical Turk to evaluate existing OCR systems before they started at building their own. If you read further into the article, they did exactly what you suggested to train their own system: "A corpus with words to use...A collection of fonts for drawing the words...A set of geometric and photometric transformations meant to simulate real world distortions...The generation algorithm simply samples from each of these to create a unique training example."