As I dutifully repaired disk permissions a few minutes ago, I wondered why they have to be continually repaired and what gets them so out of whack. For many years, I have just done the job without understanding their purpose. Will someone please either explain it or point me to a good reference? Thanks.

This is the umpteenth time that this issue has been raised. Apple has never seen fit to update Disk Utility to ignore all the "errors". Read Mac OS X: Disk Utility's Repair Disk Permissions messages that you can safely ignore. There was a whole thread on topic which I can't find immediately (someone else may be able to post a link). The upshot seemed to be that repairing permissions is next to useless.

Following are a couple of recent threads on the topic:

Disk Permissions

Repair Disk Permissions Warning

Thanks to all for the explanations. I thought I did a decent screening looking for the topic on the existing Mac OS X System Forum before posting here, but you guys are a group of walking dictionaries--just amazing. Thanks. Apparently, there seem to be a few reasons for doing Repair Disk Permissions, but not every day for sure.