The new netiquette

It used to be that netiquette was all about TURNING OFF THE CAPS LOCK, making sure that the subject matched the content, that you didn't go off the wall if someone didn't reply to your e-mail in a few minutes, that sort of thing. In fact, this (RFC1855) sort of thing. But now there are different netiquette requirements, and no obvious guidelines, nor seemingly any common practices. Now I'm just the kind of person who thinks that some de facto ruleset would be useful, so that everyone knows what to expect from everyone else.

For instance, take social networking sites like LinkedIn or Facebook. How well do you know someone before you 'add' them as a friend? Once met at a conference, once read their blog, cohabited for two years? Do you talk to them first, to let them know who you are and that you're not a crazy stalker? If someone adds you, and you don't know who they are, do you accept or reject by default? Do you ask them who they are? If they claim to have met you at $conference or in $pub, do you accept that, ask for a photo, or what?