A few years ago I got bit by counterfeit capacitors. It was a royal pain, requiring replacement of my computer's MB - and all the hassles that go along with that (e.g. plugins requiring re-authorization).
But there turned out to be an interesting backstory, including industrial espionage and treachery. A new proprietary electrolytic had been developed by one company, so a rival company got someone employed there as a janitor, who smuggled in tiny spy cameras and stole the documentation. Unfortunately, he didn't get
all the pages, so the faux formula was missing a critical step that caused the capacitors to become leaky prematurely. Dell, for one, had been duped into buying millions of 'em.