I've witnessed that a number of times -- at one company I worked with, we had a team of 30 people disabled even though all of the unit tests worked fine. Someon

I've witnessed that a number of times -- at one company I worked with, we had a team of 30 people disabled even though all of the unit tests worked fine. Someone had inserted something into some shared code (that with even marginally competent engineering would not have shared) that rendered the entire application stack inoperable. I think it was a monkeypatch (Ruby on Rails), so it was VERY hard to detect.