Yes it does happen. Small startup gets a shakedown when they get into incumbent player market. Been there. Not always but it can be game ending. Not commenting on the quoted anecdote, just my experience and word of mouth from others.
Early stage startups can run into trouble from trolls but if they do not have any money.... Unless the troll files a complaint and actually initiates a lawsuit, the scary letters should be ignored.
Though I do think startup GC's should learn how to handle the initial phases of a patent infringement lawsuit. It isn't that hard -- then it would force the trolls to spin up an expensive full-stack lawsuit if they want to keep going. This is expensive and risky for trolls.