Has anyone identified an accident that was caused
by being overweight. Are they common?

I've read of quite a few where over-weight operation combined with high
DA to result in an aircraft either running off the end of the runway on
take-off, or, worse, getting into the air and then spinning in upon
being unable to maintain a climb. I am quite convinced that over-weight
operation will cause accidents; I'm not convinced it results in
accidents as a result of structural failure.