In this article from Reuters [0] their CFO stated that they only hold a single digit market share in the travel industry.
"The possibility of antitrust issues was played down by Expedia's Chief Financial Office Mark Okerstrom who said, "It is a $1.3 trillion industry and is highly fragmented ... We are only a small player and our overall share is in single digits.""
That is like saying Microsoft Office only holds a single digit percentage of revenue in the technology sector. It might technically be true, but it is irrelevant. MS Office has a monopolist hold on the office software space.
Monopolies aren't defined by someone who controls an entire sector (a "sector" is arbitrary anyway) it is when one specific company controls one commodity or service (see Google Search, which both the EU and US have called a monopoly).
Expedia absolutely has a monopoly on travel price comparison sites now. However it only becomes an antitrust complaint when they leverage that position into other markets (e.g. like Windows with Internet Explorer, or Google with Google+).
So while I don't think Expedia has broken any laws, yet. I will say that if they started using their newfound position for leverage I'd hope the US and EU governments stepped on them pretty fast.
Ridiculous, maybe, but it shows he knows exactly what he is doing, and it should be totally expected. Peter Thiel talked about this in Sam's startup class:
"...anyone who has a monopoly will pretend that they are in incredible competition ... The basic lie you tell as a monopoly is the market you’re in is much bigger than it looks."
"The possibility of antitrust issues was played down by Expedia's Chief Financial Office Mark Okerstrom who said, "It is a $1.3 trillion industry and is highly fragmented ... We are only a small player and our overall share is in single digits.""
[0] http://www.reuters.com/article/2015/02/12/us-orbitz-worldwid...