I've heard of this with the toilets in your home also. There's a recommendation out there somewhere that you shouldn't keep your tooth brush closer than 2 meters from your toilet.
Though I can't remember where I've seen it, I know
this has been tested and disproved. The testing actually kept a toothbrush in the kitchen as a control and it ended up in worse shape than the one in the bathroom.
The more I think about it the more I think it was an early episode of Mythbusters.
We want Blue's News T-shirts!