A $50,000 education (and 6 years of college later), and do you know the piece of info I use on a daily basis???
Statistically, people are more likely to use the toilet that is closest to them, so theoretically, the toilet farthest away has been used by less people and is (hopefully) the cleanest.
Darn. I gave away my tip, and screwed up the statistics. . .but see what a useful friend I am? ; )