Is there a captcha replacement service like this

You sign up once with a website - say: ireallyamahuman.com and enter a load of captcha stuff so you can be really sure it is a human.

A website uses a simple api - similar to facebook/google login to check with irallyamahuman.com

So the captcha can just be a big button that says 'I really am a human' (so long as you are already logged in to the ireallyamahuman site) - hopefully this can all happen automatically without even having/pressing the button.

What are the cross domain p开发者_如何学运维roblems/solutions with this idea?

This will reduce the net work required to "go among the living" (crawl the web pretending to be a human). It means you only have to put one job out on Mechanical Turk (log in to ireallyamahuman.com then send me the cookie), rather than one per site (or even one per form submission for some sites)

Basically, sites have no incentive to reduce CAPTCHA work, quite the opposite.