DC, they are pissing up a flag pole.
Just because you can't exhale a cloud of vapor at a diner doesn't mean you can't vape at a diner.
This is true for existing vapers, who may be more confident and knowledgeable, however current smokers (who know nothing about e-cigarettes and aren't necessarily looking to quit smoking) may hear "You can't use these where smoking is banned, so you are still stuck outside in the cold" and think "Why bother then?"