Since this thread is still alive I figured I would post the actual response I got from the TSA when I inquired as to why my Leo was not allowed thru security when ECigs are not on the list of prohibited items.... FWIW...
From:
TSA-ContactCenter@dhs.gov
To: edited--email-address
Subject: Re: TSA Contact Us: Passenger and Traveler Information <<#410321-211684#>>
Date: Mon, 15 Nov 2010 11:46:11 -0500
Thank you for your e-mail.
Since we cannot be sure of the exact threat level at your departure facility at the time of your experience it is not possible for us to specifically respond to why your items were not allowed through the checkpoint.
The Transportation Security Administration's current security screening procedures require all carry-on luggage and accessible property be screened before passengers take them onboard an aircraft. Regardless of whether an item is on the prohibited or permitted items list, the Transportation Security Officers (TSO's) have discretion to prohibit an individual from carrying an item through the screening checkpoint or onboard an aircraft if he or she believes the item poses a security threat.
....... edited (the rest was just standard TSA policy stuff)......