My kids have them.
At first I made them wear the proper pads until they learned how to use them. They fell a bit....but no more than I did when I was learning how to roller skate. I can remember having a sore tailbone many a time from rollerskating. A few times I even fell on my butt, then bounced back and whacked my head too. I've even had my fingers rolled over while I was down! Ouch! But, I'm still here! I chalk it up to normal childhood bumps and bruises.
I think they're fun as long as they're used with restrictions and with respect to others.
Just my :twocents: