1. The internet is a public place. Some corners of it appear a little more private, but that privacy is generally very limited.
2. This means that if you change your Facebook status to engaged*, people will notice. Your mother may not be on Facebook, but I promise you will discover the how six degrees of separation theory doesn't just apply to Kevin Bacon so fast your head will spin.
3. The same applies to tweeting about your pregnancy or otherwise disseminating information. If you put it on the net, it's kinda fair game at that point.
4. Oh, and it also applies to talking smack about someone. A great (yet hard) rule is that never say anything you wouldn't want to own if it made it out farther into the world than the one person you whispered it to. I know I personally do not live up to that standard, but the deal is, you still have to. Because stuff you say, to anyone other than your cat (can't trust dogs - don't you watch those beans ads?) is going to get out. It may take a while, but it will. And thinking that being on the internet shields you is generally crap. It doesn't. You may think your friends all hate widget making and never hang out on the widget sites, but you will likely end up surprised. I used to read one blogger that in his early blogging days referred to relatives by full name. Well, it took a few years but one day they googled themselves.
5. Using fake names only helps if you have disguised the details so much that they no longer resemble reality. You can use filters and stuff to try and help.
6. Now this doesn't mean you can't ever complain about anyone ever. (It certainly hasn't stopped me.) It just means you have to be ready to face up to whatever you put out there.
7. And the final rule - if your spouse is head of a secret organization, maybe Facebook isn't the right place for you.
*I realize there are people who change their status for "fun", and that is all well and good, but again, you should probably tell your parents. Or wait and see. It's up to you.