I did the 10 miler with my wife, we saw 3 people go down! People cry about roadies that paceline or go 'too fast' but I'll take a group of 60 experienced riders going 30 mph in a pack than a gob of new cyclists going 10 mph. No one could hold a straight line, people were colliding into cyclists near them, and no one was paying attention. One girl went down face first and played it off well, but I could tell she was hurting.
The bad thing about these events is riders get too comfortable on the road. I saw too many people cutting off cars, or just wandering into the traffic lanes without looking.