Re: If CAPTCHA isn't the answer. What is?

[Anonymous Monk]

Require everyone who wishes to visit your web site to apply, in person, for a web key. Surgically embed a key-generating mini-computer just under their skin. Rig it to explode if tampered with.

That should be reasonably tamper-proof. You may have a few user-acceptance issues to work out, however...

[chromatic]

One problem with biometric systems is that they only work while you still have that body part.

[Anonymous Monk]

If the device is rigged to explode when the body part is captured, then it neatly solves the entire problem. No end user == no end user complaints! ;-)