I think two important factors might be how obvious the danger is and how useful the object is. A kitchen knife is obviously dangerous and also extremely useful, so it definitely passes both tests. A magnet toy does not appear remotely dangerous but serves little practical purpose, so it fails both tests. A laser pointer's danger is medium-obvious and laser pointers are at least a little useful, so it's sort of in between the two extremes.

If "small magnets are super dangerous to kids" was general knowledge, it'd probably make the magnets significantly safer to sell.