When workers submit their results, the requestor can choose to accept or reject the submission.

FORBES: Spam Hurts Crowdsourcing But Can't Kill It

Anyone can register as a worker but may need to submit qualifications to the requestor before engaging in the task.

FORBES: Spam Hurts Crowdsourcing But Can't Kill It

This reflects on the reputation of the worker and the requestor.

FORBES: Spam Hurts Crowdsourcing But Can't Kill It

The work requestor specifies a workload as a package called a HIT (a Human Intelligence Task) that splits the overall workload across many workers, with specified goals, instructions and deadline.

FORBES: Spam Hurts Crowdsourcing But Can't Kill It