Access iQ has published a list of the nine most common errors they run into when performing website accessibility audits - one of the worst (Captcha) is at the very end of the list. What they don't say is that Captcha's are often difficult to use by people without disabilities - is that an 'O' or a '0'? An '8' or a 'B'?
I always have a very hard time using them. There's got to be a better way - they do list some alternatives in the