I lurk on this board every day, and have learned a lot of etiquette rules that I was unaware of before, but much of it just seems like common sense to me.
I have a friend on Facebook who I knew in high school a little bit (we weren't close at all, and I never saw her outside of school), and she's currently planning a wedding. I just saw a status update from her that says "If anyone has not received our Save the Date yet, please let me know".
How many people do you think she's going to have to respond to with "Oh sorry, you're not invited."??
I'm totally tempted to message her to say I haven't received one yet....