Those self-balancing scooters that everyone’s calling “hoverboards” don’t actually hover. But that’s not the strangest thing about them—that would be the fact that this year’s most popular holiday gift keeps catching on fire.An exploding two-wheeler burned down a house in Louisiana a few weeks ago; another scooter combusted in the same state in the past week. A gyroboard caused significant damage to a home in New York a few days ago. At a mall in Washington this week, a scooterboard caught fire and shoppers were forced to evacuate. The perceived danger is significant enough that major airlines have banned the little vehicles altogether.