Just noticed this is a pretty old thread after a few minutes of typing. Not going to let that stop me, though!
I think any value would be in the novelty. They didn't seem to last very long; I'm betting it's because of the complexity of the design and the potential for malfunction given the purpose and utility.
Naw, it was because, as the OP said, some kid "accidentally" killed his sister. The "I knew it would shoot through 1/2" of plywood and I pointed it at my sister with my finger on the trigger and then pulled the trigger" sort of accident. Looks like there was a panic over them allegedly shooting through body armor, too.
It's not really that complex a of a design, just a crossbow that uses elastic instead of a prod, and a piston instead of a bolt. Sort of like a slingshot-bow. The obvious advantage is you can aim and shoot it like a gun, and the elastics give you very consistent performance. And it's more sanitary!

A regular blowgun has neither sights nor a mechanical release, so the accuracy increase should be pretty significant.
Seems like a solid alternative to a standard airgun for hunting small game, to me. Upgrade it to use the .625 Cold Steel darts, and you'd have a
great "airgun" for animals up to I don't even know how big. But someone already had to go and ruin it for the rest of us, as always.