What the "double dipping" experiment showed was that there's a drastic difference in bacteria transfer levels between "double dipping" with chips or crackers and actually spitting dip into a shared batch with your mouth. Those results are highly predictable, if you ask me! But it doesn't mean that double dipping is a proper (or even particuarly safe) thing to do at a party.
Here at home, when I have no guests for dinner, I'll go ahead and lick the spoon I stir a pot of food with, and double dip to my heart's content -- with my partner, Kevin. Kevin & I will "french" eachother, after all!
I just have to remain conscious, and not forget to forgo these habits when there will be dinner guests! So far, I seem to be successful.