Mark Kircher, a Milwaukee lawyer who is national counsel for Harley-Davidson in the case, said no two-wheeled vehicle is immune to a wobble but that motorcycles can be designed to recover from wobble quickly.
"This model motorcycle was extensively tested and validated," Kircher said. "The investigation suggests that [the wreck] was caused purely by the speed he was riding, the corner he was riding in and the [wind] from the truck he was trying to pass. He encountered a bag of concrete. That's what caused the motorcycle to upset and caused him to come off of it and get injured."
While I have no idea how much "wobble" at elevated speeds your typical Harley has, I would have to say that I mostly agree with the Blood-Sucking Lawyer on this one.
Wouldn't matter if he was on a BMW, a 'Busa, or maybe even in a car - striking an 80-lb bag of concrete (was it still "mix" - or had it gotten wet and hardened while sitting?) while fighting the turbulence in a Semi's wake, on a curve. >shakes head sadly<. Perhaps the wobble contributed to the crash, yes?
Offhand, I would say he was breaking the 12-second rule, or he wouldn't have struck the debris (attack of the 50-foot-stare is one of my own most egregious errors - but I work on it daily). It's even possible he saw the debris in time, but underestimated the ground-clearance of his machine - hard parts are usually a major limiting factor in relation to the tire's adhesion with the road, when cornering hard.
Mind, I'm not beating the man up - he's gone, and is unable to defend himself here. Having recently lost my own Father, I certainly feel for his family; one really wishes he hadn't tried to overtake the Semi where and how he did (I remember reading of this incident when it happened several years ago).