Online travel agencies (OTAs) are the fastest growing distribution channel globally, and the two largest, Priceline and Expedia, outpace the market by no small margin. Combined gross bookings of the two jumped from 38% of global OTA sales in 2011 to 47% in 2013 (see Figure 1). And the continued, super-charged organic growth of Priceline's Booking.com, as well as Expedia's assumption of the Travelocity volume largely in 2014 (and Australia's Wotif), mean global share of the two leaders will only accelerate in 2014 and 2015. The rest of the OTA market is growing, but at a pace far behind that of the big two. The sheer scale of Priceline and Expedia gives them a daunting advantage across inventory, marketing and technology, to say the least. As consolidation sweeps across the online travel landscape, four key questions loom over the horizon: 1. What do you do if you’re a tier-two OTA? In a low-margin game where scale and technology are (almost) all that matters, online sellers short on the former face a tough haul ahead. The pace of M&A will only accelerate and recast the travel distribution landscape. Companies unable to double down on a profitable niche that flies under the radar must seek new avenues to scale. Get the full story at PhoCusWright Read also "The shrinking number of traveler options"