My God what is wrong with me.
I'm now in the process of creating a code library to help answer questions like this. Anyway, here's the first fruit of this labor: how often someone will be on a flush draw given how many of a suit you have and how many are in the hand. I'm assuming any two cards right now, so real world results will be significantly different since people like to play sooted, but they're not staying in with 3[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/club.gif[/img] or whatever. I'm using a Monte Carlo simulation of 10 million hands, good enough to get it to 2 sig digits or so, as if you needed it.
So in the given hand, we have no clubs and we're 7 handed: There's about a 28% chance of someone having being on a flush draw. That's a lot less than I thought!
How many if people like to play sooted? I dunno yet, but the tighter people play, the loewr this figure will be. More testing required!