Don't know if this has been posted yet...
"Electronic/Smokeless Cigarettes on JetBlue
While the majority of electronic cigarettes may be non-hazardous, JetBlue does NOT allow the USE of them on any of our flights, but will allow them in checked or carry-on baggage. It is considered a nuisance item as small amounts of vapor are expelled from the cigarette." from Jetblue's help section
"Electronic/Smokeless Cigarettes on JetBlue
While the majority of electronic cigarettes may be non-hazardous, JetBlue does NOT allow the USE of them on any of our flights, but will allow them in checked or carry-on baggage. It is considered a nuisance item as small amounts of vapor are expelled from the cigarette." from Jetblue's help section