The IDS comes through..
Years ago, I had a spare SPARC, and being a curious fellow, I decided to deploy Snort on it and leave it running as an IDS. It never detected a single thing (not surprising as I didn't have clearance to run it, and thus it was "internal only" - and on a switched network of course).
Except for one day when it did. It detected water. A pipe above it burst and electrocuted it.