Sites owned by the big two, such as Hotels.com and Booking.com, now encourage user reviews. At the same time, TripAdvisor has launched Instant Booking, which lets smartphone users complete their bookings without leaving the TripAdvisor site (although the transaction itself will still be with an OTA or a hotel). Instant Booking serves another purpose. Half of TripAdvisor’s traffic comes through mobile devices. Being able to book in a single place will make its app slicker. Moreover, smartphones are creating firms which cater to travellers when they arrive at their destination—and TripAdvisor is getting into that business. In May it paid a reported $140m for La Fourchette, an online restaurant-booking service. On 24th July it said it was paying $200m for Viator, a firm that sells guided tours and other touristy activities. TripAdvisor’s boss, Stephen Kaufer, denies he wants to take on the big two. “We are a media site,” he says. “I want Expedia and Priceline to thrive because they are my clients.” But soon, holidaymakers will be able to book their entire trips without leaving the TripAdvisor app. Rivals beware. Get the full story at The Economist