"CAPTCHA went from relatively obscure security measure perfected in 2000 by researchers at Carnegie Mellon University to deployment by most of the major Web e-mail sites and many other Web sites by 2007. Sites such as Yahoo Mail, Google's Gmail and Microsoft's Hotmail all used -- and, for that matter, continue to use -- CAPTCHA to make sure that only human beings, not bots, could get accounts or make postings.
Those days are long gone.
By January 2008, Yahoo Mail's CAPTCHA had been cracked. Gmail was ripped open in April. Hotmail's top got popped during the same month.
And then things got bad. "