Filmmakers that don't get back to us.
Check your e-mails, people!
Of course, if you're reading this blog, then you're probably not guilty of this.
I can't tell you how frustrating it is to find a movie you like out of all the submissions. Fight for it in the competition for precious screening times. Then have the filmmaker not answer e-mails.
Every year one or two movies don't get in the festival because they never got back to us.