Answer:
Look into my face and I'm everybody. Scratch my back and I'm nobody.
I can ruin your day, or darken your life. And while I'm expected, I'm never alright. I'm bad for business, and worse for your hair. Wherever I am, there's something not there.
Kills the bad ones and the sad ones. Tightens to fit, so one size fits.
I am always hungry, I must always be fed. The finger I lick will soon turn red.
What travels from house to house and is sometimes narrow and sometimes wide but always stays outside?
What covers its face with its hands, speaks no language, yet most known what it's saying?