Do you ever start to answer a question and then think: honestly, who really gives a rat's ass what I think? I don't even care what I think anymore, so you just blow it off?
And that’s it.
Edit: Well, that’s not quite it, I guess, sometimes I do wonder, I will be “observing” or answering a question and I can see that so-an-so is composing and answer, and sometimes they seem to be composing quite a long answer and then they don’t. They don’t end up posting an answer and I always wonder why.