The 'victim' had modified the device,
First of all, I think airlines (and the TSA) need to look at homemade/modded devices of all types prior to allowing them onboard. Either carry-on or checked. There's a reason that consumer devices are given CE/UL approvals. Anything with a significant energy source could be a hazard if not designed or built to some minimal standards.
Second point: What is it with all these e-cig smokers modding their devices? I hang out on some electrical boards and they are full of "how do I mod my e-cig" questions? I suspect, given some of the boards involved and the types of people posting, that they are trying to smoke something other than the intended substance for which they need more power. Something along the lines of hash oil perhaps?