Will you give a link or a description - what are they?

Don't know what they are but just traveled from UK to Australia without them and there was no problem and have done so for the last 9 years.

Thanks for replying. They are locks that security officials can open with special keys so the locks aren't broken if your bag is searched. They can be bought from ebay amongst other places.

hi....keys tend to get into the wrong hands...even skeleton keys ( ones that open all of a brand of lock ) ...seems like a good idea as long as the skeleton keys stay only in the hands of the authorities...otherwise the lock will be recognised by others who know they have the right key for it ...and your cases could then become a target..

Got my pessemistic head on tonight...tweetie

Surely this could only happen if you left your luggage unattended?

Many cases of luggage being broken into happen after luggage has been checked in or before it arrives on the carousel. It's quite common in some countries.
When travelling to the USA I always use the TSA locks on my cases as I don't want to send my case through unlocked (as advised) or find the normal lock broken if US security decide to search my case. To OZ though you aren't going to have the same problem.
I have noticed recently more people using straps as well as locks, if it makes you feel that your luggage is safer then go ahead, but it's probably not really needed.

Judith