Insufficient Anti-Automation is fat becoming the #1 threat to web sites. Since Captcha has been proved practically useless, especially when there is a financial gain from automating access to the site, sites are pretty much defenceless against harmful automation. Techdirt's story about Craigslist losing the battle against automation tool is a very good example of this serious problem.

Read the comments, they are enlightening. As usual, one of the problem when spam is involved is defining if and what is a wrong doing and what is a  valid action. Some commenters say that Craigslist has become useless due to the spam, while others say that Craiglist is the worst censors on the Internet not letting small time businesses work. Other argue about whether this is a crime or not. 132 comments, and they keep coming 8 months after the article has been published.