If you haven't seen it already, watch the following video--it's only about a minute long, and you'll find it amusing.
Then read this article by PZ Myers. Myers is a well-known scientist, blogger, and anti-creationism commentator.
"I went to attend a screening of the creationist propaganda movie, Expelled, a few minutes ago. Well, I tried ... but I was Expelled! It was kind of weird -- I was standing in line, hadn't even gotten to the point where I had to sign in and show ID, and a policeman pulled me out of line and told me I could not go in. I asked why, of course, and he said that a producer of the film had specifically instructed him that I was not to be allowed to attend. The officer also told me that if I tried to go in, I would be arrested. I assured him that I wasn't going to cause any trouble."
The punchline is that his friend was allowed in to see the film. The friend was...Richard Dawkins.
So what does the video have in common with that story? They both show the problem with relying too heavily on blacklists. If you focus exclusively on one thing, you will miss whatever else may be right under your nose. (Think: old-fashioned spam filters, terrorist watch lists, screening for dangerous liquids on planes, etc.)