I more run into the problem with friends where people forget to un-mute their mic. I'm now in the habit of asking people periodically: "How you doing over there, [Person's name here]?" And sometimes saying: "Hey, [Person's name here]. You haven't said anything in a while, is your mic muted?" Or if I ask a someone a question and hear no answer: "If you're speaking, [Person's name here], I can't hear you. Just so you know." But the most common thing I hear is people talking with their pets when they walk by. I don't mind it, and usually ask what kind of animal they have. You know, spark a conversation. :)