0) Read Cliff Stoll's "Silicon Snake Oil" about the decline in professionalism ubiquitous desktop computing has enabled. IT Ethics is really about setting and enforcing professional standards for behavior at work. For those too lazy to read, in 1980 you could get fired for making a personal call, but in 2008 it's OK to exchange non-work email with your friends all day. Why? Answer: the office lets you get away with this in return for expecting you to answer email on weekends. Blurring the boundaries makes the rules hard to write.
1) Example: A friend called for advice, LAN manager at a 20-person company. "Everyone says the network is down, but it's actually just overloaded because the president is streaming live porn from Amsterdam." Solution: block the port, see if he has the stones to complain. Corporate ethics issues are complicated by rank and the playbook won't cover everything.
2) In 1982 at age 10 we spent a couple hours in school on telephone manners. I would hope that my own children will get the same talk, now to include cell phone, email, and web manners. Learn how to mute the ringer without answering a call. Expect that any email you send, or any web page you browse, might be printed and taped to your office door tomorrow morning.
3) Adult/offensive content makes the rules hard to write.. If I'm presenting on the big screen and get a mail notification popup for spam with a racist subject, do I get fired? Can sysadmins sue for "inhospitable work environment" because the spam was x-rated? The standards for handling these issues are related to the standards for how to behave when you're root. As I say to my dog when he's licking in the living room, "Just because you can doesn't mean you should." The standard for behavior needs to be something like "You're going to have access to a bunch of stuff, but that's no excuse for needless nosing."