One of the most successful business models of the postrecession era, sharing is increasingly under attack. Familiar to anyone who has used Airbnb to rent a home or RelayRides to rent wheels directly from a car's owner, these services have boomed by pleasing owners and renters alike. Someone whose house is going to be vacant can pick up extra cash by renting it out through a company like Airbnb; the vacationer, meanwhile, gets a bargain.
But now these outfits are getting so big that they're attracting the ire of the established industries they aim to disrupt. And regulators are getting involved...