I think motorists see a bike and mostly think "slow." And yes, we generally are slower than most traffic. But there have been occasions when I'm traveling at or near the speed limit and it seems like drivers behind me still feel compelled to pass me just before attempting a right turn.
Would something like this Speed Vest showing I'm traveling at 27 mph in a 35 mph zone help prevent right hooks? I don't know, but I certainly understand the rational behind it.