In hindsight, it's something that maybe the Mythbusters could have thought to do, but HowStuffWorks has decided to tackle the issue of the courtesy flush. You know. That time when you take an extra flush because you have befouled the bathroom more than usual.
The thing they found was that they didn't really find anything. Nobody's taken the time to find out whether it actually helps remove the odor (however many noses say it does), or whether it gets outweighed by the flush spraying bacteria all over the area (as toilets do), or the water used by a second flush removes any potential benefit, or how clogged the bowl is when the courtesy flush is done. Nobody's gone and looked. Of course, that may be a good thing, because it's not a particularly high agenda item. But you'd think something so colloquially ingrained would have been checked out by someone by now. HowStuffWorks is left shrugging its shoulders and giving the most weight to the water used by the extra flush, which doesn't really answer the question.
Again, it sounds like a job for the Mythbusters. No, we're not learning much here today, but we are at least learning what we don't know.