If drivers will plow through clearly defined signal lights at the peril of other drivers and themselves, what will they do at "Yield" signs where right of way is a matter of individual judgment? If they will generate gridlock by continuing into an intersection in spite of a red light and posted laws, can we expect them to politely wait their turn because of an unwritten "offside priority" rule which allows priority to circulating traffic?
Your roundabout article quoted Caltrans engineers as crediting the roundabout with a "40-60% decrease in accidents." Unfortunately, these statistics are about as meaningful as the ad which claims regular use of toothpaste results in "50% fewer cavities." Fewer than what? When the studies are examined more closely, they show that the only locations where roundabouts significantly lower accidents are where they replace previously uncontrolled intersections. A simple stop sign could also be expected to lower accidents.
A landmark study of modern roundabout safety by the British Transport and Road Research Laboratory (Green, 1977) compared before and after accident figures at 150 British intersections that had been converted to modern roundabouts. Of those, 60 showed an increase in either injury or fatal accidents, 26 showed no change. In fatal accidents alone, 32 intersections showed an increase, while 27 showed no change. At many of the intersections where a drop in accidents was reported, the measured decreases could not be statistically attributed to the roundabout itself.