As of early 2007, there are nearly a dozen sports-car clubs in the country that use a fractional or timeshare ownership model popularized with yachts, jets and vacation homes. All offer members the chance to drive some of the world’s most lusted-after automobiles without squelching that passion with the worries of ownership. Many of the people who join the clubs have owned an exotic car in the past. Or, they could afford one if they wanted to allocate resources that way. All understand the downside of keeping a Ferrari F355 happy and screaming.