E.g.
- Is it addictive?
- Does it have the potential to destroy lives?
- Does it have the potential to destroy lives in seconds?
- Does it have a strong lobbying mechanism behind it? (n.b. things that are good and nice rarely need someone to bribe people to accept them)
or simply:
- Would you be worried if your child did it?
I think the number of "yes" that you get draws a very clear line.