this guy got injured right where thickest part of the standard styrofoam helmet is. About half way above the eyebrow to the temple. He survived (but there was a lot of blood) but with the helmet he'd walked from the scene with a few scratches on his knees.

I'm not saying "all". But I drive about 400 miles per week (long commute) and I can say that I've seen approximately 5 bicyclist last month which stopped at the stop sign. They really stand out of the crowd.