I have never liked how quickly my CoC games at conventions sell out. Then at the table, I am not so happy about how the signed up do not bother to show up. These days, I've stopped actually running CoC games, instead throwing the word "Cthulhu" somewhere in the event's description, just avoid to fan-driven ticket buying and manic tepid showing up. I also want the "purist" to head elsewhere as well.
Check out Red Bat: Cthulhu and if you show up at my "Cthulhu" games with a printed copy from your laser/bubble jet printer, you get a free ticket into the adventure.