Social media is a phenomenal thing. It's an effective way of getting across your thoughts to a community of friends, acquaintances and even strangers, without being obnoxiously intrusive. The only rule being: Respect everyone's opinion; if you don't like a sentiment posted on somebody else's wall, don't read it. It's as simple as that. But there will always be those who can't fight the itch to argue and flame, not realizing that they are already bordering on rudeness.
But bad manners in cyberspace aren't limited to downright belligerence. Too often, an act of disrespect is committed every time one posts a comment on a thread that is completely out of topic. It's like saying: "I'm too cool to join your conversation, so I'm going to ignore all of you and start my own subject matter." There's nothing wrong with kicking off your own talking point--as long as you do so separately.
Check out the dude below, who posted a totally unrelated comment on a Lexus Facebook page thread in which the luxury Japanese carmaker did the asking.