cockroach effect
n.— «It’s sort of like what they call the “cockroach effect” on the financial markets. Every time there’s “hints” of anything going wrong inside a company, everybody starts selling the company’s stock in a knee-jerk vote of “no confidence.” A sign of “bad news” (whether explicit or implicit) may very well be just “one cockroach” popping up at the surface, while underneath the surface is a whole colony of cockroaches and numerous deeper problems about the company in question.» —“String Theory by Press Release” by JC Not Even Wrong June 22, 2004. (source: Double-Tongued Dictionary)