How unsanitary is double dipping anyway?

Double dipping—practice of dipping a chip (or cracker, carrot, or anything other food that can be dipped) into a dip, then biting onto it, and dipping it again with the bitten side down (dipping a non-bitten corner of a previously bitten food does not qualify as double dipping)—is widely frowned upon and considered, aside from plain gross, unhygienic. But how bad is it, really?
Read more: http://qz.com/795359/how-unsanitary-is-double-dipping-anyway/?source=Snapzu