What's to stop someone using this to 'outsource' CAPTCHA solving? (Not that spammers need any help doing so!) I signed in with my normal Amazon account and had

What's to stop someone using this to 'outsource' CAPTCHA solving? (Not that spammers need any help doing so!) I signed in with my normal Amazon account and had a look; it seems to be full of bloggers paying tens of users a couple of cents to blog about their URL or add it to social networking sites. As a blogger that relies on genuine traffic and social bookmarking, it makes me despair.