So what comes to mind when you see someone dip their chip into a salsa bowl, take a bite, then dip it again? The majority of reactions are negative. Everyone assumes that by double dipping you are basically contaminating the dip for everyone else. Here is a small clip showing just that:
Now after doing some research, I was able to find out that in actuality there is already more bacteria in an average container of salsa then what someone could possibly add to it with just a simple dip of a chip. The amount of bacteria that is added are microbes (tiny) in size when compared to the large amount already in the store bought container. So if you are looking for a bacteria free can of dip, you are pretty much out of luck. If you want to keep it as bacteria free as possible, then you had better keep that bowl to yourself.
So the next time that you see someone double dipping, try not to give them too hard of a time. Shoot, you can even go ahead and do it yourself. I know the feeling when you have half a chip and no salsa... Now you can stop worrying and indulge yourself knowing that it is not going to hurt anyone else.