For instance big travel agencies have a lot of complaints (including fraud). In my case EXPEDIA ruined my trips and tried to keep (steal is the right word) the money for services that they failed to provide. Just search for "EXPEDIA complaints" in Google or Yahoo and you will read horrible stories from people that used EXPEDIA. A similar search using other online travel site will give you similar results.
Most people wont search for complaints regarding a company but would tend more to search for 'reviews' which can be controlled by a company if the reviews are on their own website.
Good marketing is usually more important for bottom line than good customer service (not if most of your business is from repeat customers, obviously)
Expedia probably books thousands of vacations a day, of course you're going to have a few go wrong. That doesn't make them a bad company, and all the satisfied customers recommend them to their friends. That's how they stay in business.