I like how he proudly claims to have been advocating this issue since 2005, then begrudgingly writes that it has never been an actual problem in ZipCar's history.
You buy insurance mostly to protect against costs that are expensive and unlikely to happen. The article points out that in New York, which has a lot of Zipcar customers, 3 percent of bodily injury liability insurane claims are over $300,000. So although no Zipcar rental has yet resulted in such a claim, it still seems like something worth insuring against.