In the early days of the Internet, services such as eBay and Craigslist revolutionized secondary markets, making it easy for individuals to buy and sell used goods. Among other devastating results, the classified ad went the way of the dodo (and with it much of the revenue that subsidized printed newspapers). Now we’re in the midst of the next generation of such services, which make it possible for individuals not just to dispose of used assets but to rent, lease, or loan their belongings to other consumers, without the need for much if any corporate infrastructure.