Sorry about the delay... I have the reply from my friend about the FAA concerns:

"The FAA is concerned about anything in baggage (carry-on or checked) that could heat up and start a fire. Obviously a fire in checked baggage is worse because you can't get to it an put it out.

Something like a flashlight or radio is not so bad. If the flashlight is left on, the bulb will heat up but it is kept from touching any clothing by the plastic lens (believe it or not, there is a US standard that a flashlight cannot ignite clothing). Same with a radio, even on, it won't start a fire.

With the bike light, there is no standard for no ignition of clothing. You could do an experiment - turn the light on for 5 minutes and then drape an old sock over it. My guess is that the sock would at least smolder.

Anyway, right now it's OK to put the light in your luggage. However, I think there will be a new rule against it shortly."

I hope this can answer any questions you may have. If not, I'll ask him again!