meeni has hit it spot on  - for walkups, their rooms are so tiny that you will always be able to keep an eye on your stuff.
(It's been a while, but) last year I quite often mongered with a backpack full of all my good stuff - cameras, laptop, ipod etc... because I would combine mongering with the usual touristy sightseeing stuff. Not only are the rooms small, but I found that the walkup girls want to get in the shower with you and clean you - good fun, but this is also the time I am usually wary in other countries - you're washing off your little Bro after a session while they are going though your stuff  . Generally not a problem in HK, but something to be aware of.
HK mongering is pretty easy in regards to security. Just be aware of when you cannot see your bags, but in general, no problem. I'm even going to go out on a limb and say that the gals are not interested in your passport, bankcards etc... anyway. At most, they might grab a few notes if they see them. | |
- for walkups, their rooms are so tiny that you will always be able to keep an eye on your stuff.
. Generally not a problem in HK, but something to be aware of.