Yet they will allow you to use a Laptop, portable DVD, Gameboy,
electric shaver, etc. All of these will put out as much if not more RF
interference than a scanner. If the airplane's navigation system is so
suceptible to RF interference, what's stopping terrorists from taking
advantage of this by using a scanner secretly, say in their pocket with
an earpiece? Or, does the scanner have to be seen by the flight crew
for it to have any ill effects?

I don't hear computers, DVDs, Gameboys, and shavers over a block and
a half away in my car on VHF and UHF, but I can show you areas where
I CAN hear the LO of a scanner 'sweeping by' when I drive through
at that distance.

It's not ALL scanners. Some are worse than others.

Heck, I've gotten permission to use my 2M ht in flight, as long as I
promised
not to transmit, and advise the captain when I turned it on AND when I
turned it off. (I assume he was actually going to look at things to see if
he
could detect any issues.)

Stop whining, keep the scanner shut off when you fly, unless you are in a
private place and the pilot in command says it's ok.