Yesterday, while searching for Web Services on the Internet I came across an old, popular web service called “Amazon’s mechanical turk” based on the mechanical turk trick from old magic days.
The gist is, you (“The requestor”) put in a HIT (Human Interaction Task) in amazon’s lingo so that some one on the Internet can solve it for you (“the worker”). Most of what I saw on the website seemed like random tasks being used by researchers, online yellowpages-like directories, marketing, classification of goods, etc.
What might also be an interesting application, and I’m sure it’s probably being used for is, captcha-solving for spammers.
Also, the Amazon Mechanical Turk terms of service don’t help and say the following (verbatim):
Amazon Mechanical Turk provides a venue for third-party Requesters and third-party Providers to enter into and complete transactions. Amazon Mechanical Turk and its Affiliates are not involved in the transactions between Requesters and Providers. As a result, we have no control over the quality, safety or legality of the Services, the ability of Providers to provide the Services to Requesters’ satisfaction, or the ability of Requesters to pay for Services. We are not responsible for the actions of any Requester or Provider. We do not conduct any screening or other verification with respect to Requesters or Providers, nor do we provide any recommendations. As a Requester or a Provider, you use the Site at your own risk.

Given this, and the rates prevalent (about a penny or so per task), I think spammers might have a free-run on this service. Of course, amazon has a conveniently available web service available at http://mechanicalturk.amazonaws.com/AWSMechanicalTurk/AWSMechanicalTurkRequester.wsdl.
Now, the key question is, suppose a spammer uses this service, who’s to blame…I wouldn’t imagine the solvers know what the intent of the act is, amazon (possibly) can’t be liable because the ToS is required to be accepted before use, and since the requestor is somewhere on the Internet, he/she possibly can’t be traced.
Of course, I’m not saying that Mechanical Turk is all bad, but like all walks of life there’s a positive or a negative use to everything.
As someone once said: “Every tool is a weapon if you hold it right”!