Car sharing - a model of car rental where people rent cars for short periods of time... The main factors driving the growth of carsharing are the rising levels of congestion faced by city dwellers; shifting generational mindsets about car ownership, the increasing costs of personal vehicle ownership... according to The Economist, carsharing can reduce car ownership at an estimated rate of one rental car replacing 15 owned vehicles.
Similar idea is possible for other forms of transportation, such as a yacht.
Wife-sharing - e.g. site "SexWife ", Polyamory, swingers, etc.