A genuine nail-biter

I sat at the conference table yesterday--it was a pleasant conversation, a business meeting. Two men sat across from me, one beside me. We were all discussing a pretty technical process.

About five minutes into the conversation, my attention was shaken by a flurry of movement to my right. One of the guys across the table was voraciously munching his fingernails. I tried not to watch because I don't think I could have properly reigned in the expression of shock on my face. The enthusiasm that he was putting into it really threw me off--it was comical, but a little alarming.

I averted my eyes, but, observing him out of the corner of my eye I noticed him biting each nail on his left hand one by one, even flipping his hand in different orientations just to ensure he had thoroughly and properly gnawed it to a stump. I didn't look to see if he was saving the pieces or not.

Was he nervous?

Just a habit?

Why didn't anyone else notice? ...Or did they?

Am I going to shake this guy's hand when we are finished? If so, where is the nearest soap and water?

Is he bored and needs to occupy his time? (just for the record, I wasn't the one talking)

He paused, making a loose fist and turning it over to admire his work. The meeting continued.