There's a lot of talk out there about Facebook etiquette but not a whole lot of talk about LinkedIn etiquette because in some ways, there's a lot more weirdness to it, mainly in that while Facebook is supposed to be silly and fun-- something that lends itself to child-like behavior-- LinkedIn is supposed to be serious and professional. Which brings up the question of what does it mean if you never get a response to a query about adding somebody to your contact list? Is it because they use an old email address and they don't get it or never check LinkedIn? Possible. But you can't help wondering why you don't get certain people to respond. Like if an old boss doesn't want to link with you. Is it because despite all of the nice things they said about you, they really thought you sucked? And what about the coworkers who you thought you had a good relationship? Was the good relationship not so good?