I was riding in Suasalito one fine day, enjoying the scenery, when all of a sudden, one of those "extension" things (never knew what they were called 'til you brought this up) came out of nowhere, and like the Titanic, I plowed right into it, did an endo (still clipped into my bike) and landed spectacualrly into a bush. I messed-up my right thigh real bad, and had to ride home (50 miles away) with blood running down my leg. Fortunately,a good samaritan saw my bloody mess from his car, pulled over, and whipped-out a first-aid kit and bandaged me up (thanks guy!
).
But yeah, those extensions suck.