People either want to be entertained or see something which is like a commercial.

So, a movie should either be a true work of art. (like those feature movies), in which the message you want to pass is gently hidden.

Or- very blunt (like a commercial)-a short movie with a very clear message.

http://www.youtube.com/watch?feature...klKyFMUME&NR=1

Although people tend to be suspicious of what looks like you want to sell them something.

Some messages can be passed very well by creating a contrasting message.

http://www.youtube.com/watch?v=rsP0vNPAxFs

Irony is many times a good way to make people think.