Yes, I was talking about diacetyls. It's good that you try to avoid them, but do you know you're actually avoiding them. The whole Mother's Milk thing illustrates my point and shows that we need to know what is going into these things.
Maybe I'm wrong, but I have heard a lot of researchers and medicals professions who say that e-cigs appear to have no apparent short term effects, but they are still worried about long term effects.
Finally, coffee has had a lot of research. From my understanding, coffee itself has never shown any long terms effects since it is a pretty simple stimulant, much like nicotine. Obviously all the cream and sugar we put in it are going to be bad, but that's common sense.
Coffee and Health | The Nutrition Source | Harvard School of Public Health
This study followed people for 18 to 24 years. I'd say that long term.