Stats old car accidents and kids:
All these things may seem ridiculous, but doing so would have greater impact for child safety than banning rare earth metal balls. Children lives would actually be saved.
The government isn't banning magnets, just like they didn't ban darts. You can own magnets. You can own small round magnets. You can own them in sets of 200. You can even sell them! You just can't set up a business marketing as a toy something the CPSC believes will needlessly endanger children.