I know I shouldn't subject others to my terrible singing, but it just happens.

I came across a list from from iVillage about the things you shouldn't be doing in public.  There were some things on there that I agree should be done in private where the rest of the world doesn't have to witness it.

One of them was singing with your headphones on which is the same as singing in public.  I do it in the car, at the store, wherever I am and a song I know comes on.  Now I understand why people look at me funny!

What's something you do in public that should be done in private?