A local family donated a Quadra 840AV to our middle school. (It's an ancient model, but one teacher still had a use for it since she just wanted to let students use a set of reference CD-ROMs.) Anyway, I decided to give the system a once over before putting it in a classroom, even though it already had Mac OS and a couple of applications installed and seemingly working fine. I'm glad I did. The web browser cache was full of porn. And there was also an address book with names, addresses, phone numbers, dial-up account numbers, etc. Needless to say, I decided it was worth the time to do a low-level zeroing of the disk drive and to reinstall all software!
Repair people don't have a reason to snoop, but people who donate a computer should expect somebody to be looking at what's there. How could people donate a computer like this to a school without thinking about what's on the system?