I've had the same experience, although I have always managed to simply brake out of trouble since I anticipate that the motorists I encounter are either stupid or full of malice. When I have caught up to the truck drivers who have done this, invariably the reason they pulled out was that they misjudged my speed. They're used to cyclists who toodle along at 10 mph, and someone riding 20-30 mph just doesn't register for them.

I've even had car drivers do this to me when I'm driving a truck. Yes, they pull out in front of 80,000 pounds of death because they are not able to accurately judge the speed.