I have personally seen some folks that shouldn't be allowed to ride.
Nitwit #1- 21 year old college kid, riding home from class in shorts, tank top, flip flops, but he WAS wearing a helmet!

Super-genius decided that it was cool to gun his crotch rocket and pop wheelies in the middle of traffic. 40 mph two lane road in a major residential area. After two, he pulled a third, but twisted the bars on the way down, and immediately started a nasty snake. Only stopped when he slid up into the curb, he kept the bike up, but lost a flip flop and skinned the hell out of the bottom of his foot. Seat of the bike is still missing, genius still walking funny. Worse yet, he has done this before, and dropped the bike twice, with missing lower fairing sections on the bike that he is too poor to replace.
Nitwit #2- Group of Hayabusa jockeys were tearing down Hwy 635 in Dallas on a Saturday night. Traffic is running 65 to 70. Said group of rocket scientists decided to start pulling wheelies in traffic. 635 is always PACKED with cars. As soon as I saw the oxygen thieves attempting to temp fate, I changed lanes, so I wasn't immediately behind them. Not but a minute later, one of them pops a wheelie, goes vertical and drops the bike in the left lane. Said genius was VERY lucky, he slid off onto the left shoulder along with the bike, which hit the concrete median. Bike was trashed, idiot boy lost some skin and cracked a shin.
Much as I DONT want Uncle Sugar getting involved in regulating our lives, I have to agree that kids on 160+ HP bikes is just a stupid risk. Only 1 guy in 10,000 can ride a bike like that to its theoretical limits. Most average 20ish riders don't have the skills, experience or JUDGMENT to really operate a bike like that in public.
Ironically, in a lot of cars, cash limits the amount of stupidity these guys can get into. While there are a lot of cars that will run north of 400+ horsepower, they tend to price themselves out of the "young kid" market. Hot rodding their rice burners costs money, and shrinks the market down considerably. The high performing sport bikes are CHEAP, and most kids pick them up used for under 10K.
I think EVERYONE that rides should have to take the rider safety class. Let them get some time and experience on bikes before you start having them jump onto monsters they can barely handle. That saves them (and us) from the unpleasant consequences of too much speed + too much testosterone + too little judgment.