I've only written two screenplays, one with another author which made it to the last round of elimination in a national contest, and one for fun. I will be the first to say that I am not a natural screenwriter. Screenplay writing is damn hard, for one thing, and requires much more self-discipline than novel writing.
For those of you interested in writing for the screen as well as print, check out screenwriter/novelist Lee Goldberg's weblog, A Writer's Life. One of his recent posts, "Is a Story Really Necessary" is so funny you should not drink beverages while reading it.
My solution for the story-challenged screenwriters? Send them over to use the Plot-O-Matic.