I do believe the Hurt report is where that stat is from and that there may be more single vehicle accidents now (bikes). What hasn't changed is that cager pullouts and left turns in front represent the majority of bike v. cager crashes. As for single bike accidents, I'd think getting into a corner too hot and riding under the influence are the biggies.
Yep - experienced sport bike riders out pushing their limits and exceeding them. New, young sport bike riders who don't know their limits. And another big group, apparently, are middle-aged re-entry riders who haven't ridden for years, and have bought the largest, heaviest, most powerful bikes they can afford. I fall into the first of those categories - I've "crashed" twice, although only one was a typical too-fast-into-the-corner, the other was an extremely slick corner in the rain where I had to hit the brakes part way through to slow down for the tractor that was pulling a Honda Civic out of the ditch. That corner was so slippery in the rain that I could hardly stand on it. The first "accident" I don't have any excuses for. Neither resulted in any injury to me or involvement by the cops, however.