I plan on picking one up for a trip out west where my CCW doesn't reciprocate and they frown upon knives. It's not my ideal choice, but if the laws of the land are going to disarm me, then I might as well pack something to defend myself with.
They have their place, but that place is when a more serious self defense item can't be brought into play. I think they're great for LEOs. It allows a police officer to control an escalating situation without having to use deadly force or potentially be injured.
For civilians, though, I dunno. Yeah, if someone is trying to mug me, I would rather have 7 rounds of .45acp than one shot of TASER barbs. Pacification isn't my job. Surviving the situation is.