Travel monopolies include Airbnb.com, Expedia, and Booking.com.
These are platforms that may have been considered "decentralized" in the past, but a look further down sees that they are far from them. Before booking online, brick and mortar travel agencies were the most popular way to book flights and accommodations. The big hotel companies had the advantage of connecting full monopolies to particular travel agencies, adding large percentages of commissions to intermediaries who would book everything.
Online platforms like Expedia.com and Booking.com are not very different, but they offer a few more options and have tightened the ship. Then came Airbnb.com, which made rental spaces easier and more affordable. He alone has upset the hospitality industry by offering people another option more p2p