Beyond having kids who regularly eat off the floor (mostly just what they dropped there at meal times that we missed cleaning up, but sometimes things I simply cannot identify that were hiding under a cupboard door or the ottoman, etc), but most of us have grabbed something that dropped on the floor at some point even as an adult.  In any case, I thought this brief article was interesting enough to share:

http://ca.delish.com/food/recalls-reviews/five-second-rule

Contrary to that article, it should really be called the "0 second rule", because there won't be a significant difference between 3,5 or 10 seconds.  What truly matters is the contamination of the surface, because bacteria will transfer almost immediately.  http://www.nytimes.com/2011/03/01/science/01qna.html

I guess the question you should ask yourself is, "Would I lick this floor?"  Cuz that's what you're doing.

Good point Diddly, that's why I rarely eat things that have been dropped on the bathroom floor!

Note Danmick said "rarely", but not "never"...
That's probably due to this entirely fictional story that I'm making up but is quite possibly something that really happened at some point...  I remember seeing Danmick licking up what he later claimed "looked like peanut butter.. but didn't really taste like peanut butter" off the bathroom floor.  He followed that up with the comment "but it sure was crunchy.. and hairy!".  He claimed that the 3 or 5 or 10 second rule did not apply since he did not know how long it had been on the floor, but he did remember arguing about it with his sister back when they were kids!
;P