There is no doubt - spammers are becoming cleverer every day. I've added CAPTCHA verification to my site in order to prevent spam comments from being submitted. It really helped - previously I used to remove about 10-20 of them on daily basis, offering everything from child pornography to grey mortgages. However, even after the new safety measures have been introduced, I still get a couple of comments a week, which were created by spammers. Somehow they manage to break CAPTCHA. In addition, they texts are quite long, compared to the traditional "go-to-this-web-site-and-buy-stuff" ads. They seem vaguely related to the content of the actual article to which they are added. I suspect some graduate or Ph.D. student, involved in Artificial Intelligence (AI) studies, has written a program to both analyse the text and to bypass the filters. Well done, mister hacker.