Skater boy here. Wish he would find something else to breathe besides skating.
Mine's a roller blader and I can so remember when I felt the same way you do.
On the positive side, it's good exercise, inexpensive, ecologically sound transportation, and skates/skateboards are much less likely to get stolen than bicycles.
We've never had any sort of serious skating injury, but I do highly recommend that you provide your son with a set of wrist guards as well as his helmet, as wrist injuries can be very common, painful, and preventable for skaters.
My 15yo nephew skates. Skating actually helped him get away from some kids who were a BAD influence, and save himself from a downward spiral of drug use and drinking. The skateboarding crowd seems to be a little more grounded as far as that goes.
Like the PP says, it's good exercise, and if you have a skate park nearby you know where your kid is and what he's doing.
My boys are only 2 and 6 but they both already skateboard/scooter (well, the 2 yo "butt boards". My 2 yo is talking about the skateboard park. And guess why, because my 44 yo DH is obsessed with skateboarding. We were at a family gathering and I left his skateboard there and oh boy, was he upset. Luckily someone found it and he got it back. DH goes to skate parks. When we drive to Wisc, we always have to make a stop at a skate park in Chicago. All the kids at the skate park think he's pretty cool and really like his "old school" board.
we've got a gaggle of 10-13 year old boys (mine's 12) that are going crazy for skateboarding lately. the 2yo wants to be in there with the big boys soooo badly! sorry, fella, a few more years for you, i think...
um, my dh obsesses about skatebords. he is 41.