The Straight Dope on the toilet flushing spray facts.
But HERE is my FAVORITE PART:
As Professor Gerba's research would later determine, however, the bathroom was hardly the most dangerous part of the house, microbe-wise. The real pesthole: the kitchen sponge or dishcloth, where fecal coliform bacteria from raw meat and such could fester in a damp, nurturing (for a germ) environment.
Kitchen sponges and dishcloths are scary and awful. Also, while I'm at it, these kind of enclosed toothbrush holders are the devil, and exist only to fill with germy green sludge. Never use them.