A nickel says I am human
The ways of getting around CAPTCHA are well-known: employing a dedicated person to solve it, asking porn surfers to solve it, asking clever computer scientists to write a program to solve it. The marginal cost of breaking a CAPTCHA in each case is less than a nickel and probably less than a cent in bulk. So you can easily buy your way into services protected by a CAPTCHA.
On the other hand CAPTCHAs are annoying, especially as the arms race causes them to become more complicated for humans to solve. They are a huge user interface problem. And last, but not the least, they discriminate against disabled humans.
Why not just ask users to pay a nickel directly instead of solving a CAPTCHA? Because we don't have any good way to charge a Web user a nickel, or to verify their reputation. So let's fix the underlying problems—the Responsibility paradox and the Compensation paradox—and bury the ugly hacks. (This post is sloppy—please read the follow up)