Quote Originally Posted by Paladinleeds View Post
Bots will adapt and become more advanced and solve the captchas. If I remember rightly, there already exist bots elsewhere that can solve captchas (audio and visual). It would halt the bots for a while, but they'd quickly adapt to it and it'd be back to business as usual.
This is akin to saying you shouldn't test for anabolic steroids in sports because there are more sophisticated PEDs that won't get caught that way. Yes, CAPTCHAs can be defeated by a sufficiently motivated attacker. The idea is to raise the bar, though. Provide enough of an obstacle that you exclude the less sophisticated cheaters and I believe you'll find that the more advanced programmers have better things to do with their time.