How robots and spiders are causing issues, how to stop them. We can also talk about Completely Automated Public Turing Test To Tell Computers And Humans Apart - their use, their compliance issues, porn proxies, PWNtcha and other ways to defeat them.
this reminds me of knuth's story about when he thought he could create a good random number generator by making a ridiculously complicated algorithm. after very little analysis though, he found that it had very short cycles and even a fixed point if i recall correctly. the point being is that often times you can't just throw in some additional complexity to make something more secure. a much better approach is to come up with a cleaner design. now i'm not saying a good javascript based captcha is impossible, i'm just saying you're not going to end up with one by adding additional complexity to an already known weak one.
