There are two important questions that need to be answered about second hand electric cigarette smoke?
Does second hand electronic cigarette smoke contain any nicotine?
Does it smell?
If the answer to both these questions is no, then there is no reason to ban e cig usage in any environment.
Studies have shown that you will absorb about 99% of the nicotine you inhale. So you will exhale trace amounts of nicotine but at a percentage that is to small to matter.
Personally I notice a slight smell when I breath exhaled e cig smoke but its very faint and not offensive.
Hopefully more airlines and other public places will recognize there is little harm