A person who's on the chopping block is in danger of losing their job or getting into serious trouble. A project that's on the chopping block is likely to be terminated.
Matt really put his head on the chopping block when he started
v. Thread crapping occurs when a person comes into a thread and posts something contrary to the spirit/intent of the thread, often derailing the discussion or turning it into an argument.
Coming into a thread titled "I love my new Apple Macintosh!", and posting "PCs are better and cheaper" is thread crapping.