Not to intrude or nitpick here, but...
Actually, the *minimum* time of boiling to have "sterile" (and I use those quotes on purpose) liquid is 30 minutes. 15 minutes will definitely make sure that *most* of the nasties are gone, and that's especially true if you heat shocked them by sending them from cold (less than room temp) to hot. However, anything less than 30 minutes risks infection, though it's not too likely, as the yeast you pitch has a chance to out-compete the wild yeast for nutrients.
Bacteria, though, are a whole new ballgame. They replicate *much* faster than yeast, and can take over a culture (i.e. your wort) before your yeast has a chance to blink.
I'm sorry. I majored in bacteriology and genetics in college (micro-biology basically).
Again...I don't like to be "one of those nitpicky guys" but if you want to be sure of "sanitary conditions" boiling the wort for 30 minutes, minimum is the way to go. Like I said though, it'd probably be ok at 15 minutes if you heat shocked it.