The new rules come following a study highlighting the dangers of wayward drones. A smaller drone isn't necessarily safer than its larger alternatives, for example -- many of those more compact models have exposed rotors that can do a lot of damage. A drone weighing around 400 g (0.88lbs) can crack the windscreen of a helicopter, while all but the heaviest drones will have trouble cracking the windscreen of an airliner (and then only at speeds you'd expect beyond the airport). While you might not cause as much chaos as some have feared, you could still create a disaster using a compact drone.
It's nothing new to register drones, of course, and it doesn't appear to have dampened enthusiasm in the US. The test adds a wrinkle, though: how willing are you to buy a drone if you know you'll have to take a quiz? The test likely won't slow sales too much, if at all, but it could give people one more reason to pause before buying a drone on impulse. Manufacturers appear to be in favor of the new rulebook, at any rate -- DJI tells the BBC that the UK is striving for a "reasonable" solution that balances safety with a recognition of the advantages that drones can bring to public life.