I don't think I've killed a thread yet, but I've had my "screaming into the abyss" posts.
You know when you make a post that you think is cool, or funny, or really makes a contribution and the discussion just passes it by.
It's probably just a function of my social insecurity, but I always find myself second-guessing myself when that happens. My logical side points out that conversations shift and flow, other things come up and so forth. My shy, insecure side is convinced I put my foot in it and people are being too nice to say anything.