The right time (maybe): A man in Canada locked himself in the bathroom of a Greyhound bus. When the driver forced the door open, the guy had blood running down his face from ripping the skin off his scalp. The police used a taser on him because he was violent and a danger to himself.
The wrong time: A guy in Pennsylvania was sleeping on the couch in his own home when the police, responding to a silent alarm, tased him. They tased him twice more after he showed them ID to prove he lived there. I'm sure there's more to the story but still - why so quick to taser?