I never saw "Expelled" advertised on TV, nor have I seen a billboard or any print ad. When I asked a few of my co-workers about it, none of them had heard of it.
I know about it from reading the JREF forum, and seeing a few articles on skeptical or science related internet sites. This isn't a movie that is breaking all records. If I still had kids at home or was still involved with all the orgs I used to be involved with, I wouldn't have time for even these, and likely the existence of the movie might have gone completely unnoticed. I am not an ignorant person.
Ben Stein might have politics or viewpoints you don't agree with, but he is a very educated and intelligent person. He has a law degree (regardless of what you think of lawyers, you still have to have some intelligence to get through it), and is an economist. He advises on stocks, has had character roles in movies - but that's not his 'career'. He is known as being one of the intellectuals in Hollywood where a lot of 'movie stars' are high school drop-outs. He also happens to be a practicing, non-secular Jew, which I add to refute posts I read elsewhere referring to him as a Christian fundie. I used to read a column he wrote, which was about his life with his son and wife, his grandparents and their life in Europe, the shallow people he meets in Hollywood, and so on. He comes across as witty, honest, and likable. From what I read about the movie, I would of course strongly disagree with his position, but I can't speak negatively about him as a person or throw the word 'stupid' at him.
And I don't think less of two very-harding working entertainers because they are not current on B-grade movies.