Lowering speed limit saves money(Gas), but thats debate for another thread. Banning thing costs us our personal freedom. Also personal responsibility goes out the door. Reason why we can't have things like chemistry sets like our parents had.
The only personal freedom being lost here is the freedom to market "any aggregation of separable, permanent magnetic objects" as "a consumer product intended or marketed by the manufacturer primarily as a manipulative or construction desk toy for general entertainment, such as puzzle working, sculpture, mental stimulation, or stress relief".
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.