Amazon Mechanical Turk vs CrowdFlower: What are the differences?

Developers describe Amazon Mechanical Turk as "Programatically access thousands of high quality, low cost, global, on-demand workers". Amazon Mechanical Turk is a marketplace for work that requires human intelligence. The Mechanical Turk web service enables companies to programmatically access this marketplace and a diverse, on-demand workforce. Developers can leverage this service to build human intelligence directly into their applications. On the other hand, CrowdFlower is detailed as "Instantly hire millions of people to collect, filter, and enhance your data". CrowdFlower is the world's leading crowdsourcing service, with over 800 million tasks submitted by over four million contributors. We specialize in microtasking: distributing small, discrete tasks to many online contributors, assembly-line fashion - for instance, using people to check hundreds of thousands of photos every day for obscene content.

Amazon Mechanical Turk and CrowdFlower can be categorized as "Crowdsourced Labor" tools.

Some of the features offered by Amazon Mechanical Turk are:

• Tag objects found in an image for easier searching / advertising targeting
• Select from a set of images the best picture to represent a product
• Audit user-uploaded images for inappropriate content

On the other hand, CrowdFlower provides the following key features:

• RTFM- Real Time Foto Moderator: crowdsourced image moderation with a simple, real-time API. (Originally known as the Image Moderation API.)
• Business Data- Collect data on businesses at massive scale
• Customer and Lead Data Enhancement- Increase sales by knowing more about your customers