Just checked. As others have suggested, it's definitely possible to lock yourself out good and proper. I opened the boot using the centre button while the car was parked and locked up. Put some stuff in and (making damn sure the key was in my hand) closed it again. Thunk, it locked.
This is scary stuff, me definitely no likee. For goodness sake, I never heard of anyone having stuff nicked from their boot while they were with their car. If you do see dodgy characters hanging around, then actively choose to lock the boot, it's not hard.
How do you turn this ghastly feature off? Will the one-click lock/unlock do it?
I think it's insane even as a default, and as a non-customisable feature, well, who do I shoot?
Rolfe.