In Empire, when C-3PO wanders into a machinery closet after hearing what sounds like an R2 unit, he becomes the first of the group to learn about the presence of the Empire but gets shot to pieces right away by the Stormtrooper already in the closet*. Ignoring for the moment the debate about whether stormtroopers are or aren't idiots, why was C-3PO shot right away instead of being captured and questioned? Surely Threepio wasn't a credible threat to a the trooper, who should have realized either (a) that the droid had accidentally wandered in there and just needed to be shooed out or (b) that he held important information and should be captured. (Of course, given how bad he is at keeping his mouth shut, I suppose it turned out just as well that he wasn't functioning and able to give away his friends. That could have turned out very badly.)
*The shooter is never shown onscreen, but we know it's a Stormtrooper from the comments C-3PO makes as he's being reassembled by Chewbacca later in the movie.