There have been news stories recently about the germs that get on such items when kept out in a bathroom. When you flush a toilet, the water particles actually "swirl" about the air in the bathroom and get ONTO things like your toothbrush.
Also, replace your toothbrush every time you are sick! My old old family Dr taught us that! Thanks Dr. Grant! I have over-sensitive teeth, so can't use a Sonic care (hubby does). Just regular old brushes for me and my teen daughter. We get the multi packs at Sams Club usually, so we always have extras. I brush alot (sort of anal about it like handwashing), so I replace mine about once a month anyways.
This is taken from WebMd
Don't share toothbrushes.
Make sure everyone has their own toothbrush by color-coding them, Schachter says. "Don't let your toothbrush make contact with any other toothbrushes stored in the same holder either. Germs can be passed along that way," he says. "A good rule of thumb is to keep them at least an inch apart." Replace your toothbrush regularly after you've had any illness such as a cold or flu because germs can remain even after you've recovered. Here's why: When you brush, you remove plaque and particles so toothbrushes can become contaminated with bacteria, blood, saliva, and oral debris. This contamination can be passed right back to you.
Always flush with the lid down.
According to Charles Gerba, PhD, a professor of microbiology at University of Arizona in Tucson, flushing the toilet with the lid up is not wise. "Polluted water vapor erupts out of the flushing toilet bowl and it can take several hours for these particles to finally settle -- not to mention where," he says. "If you have your toothbrush too close to the toilet, you are brushing your teeth with what's in your toilet."
I personally store mine is a drawer. Hubby has a drawer, and I have my own. Teen daughter has her own as well...downstairs in her bathroom. All sperate, and away from toilet swirling water particles! Ishy!