Last October I took a bare hard disk drive through Heathrow security and they had me extract it from my luggage to dust it down for explosives. Earlier this year, again carrying a bare hard drive, I just took it out of the bag and put it in the tray with my laptop. That went through with no problems.
Sounds like an ideal way for them to slurp data for free - if you can't power up the drive yourself, they can offer to connect it to their system, which would probably read as much as it could during the test period.
Biting the hand that feeds IT
