> For the most availability, best prices and service,
    > always book directly with a hotel. 

(Full disclosure: I work for Booking.com an online hotel booking website and Expedia's competitor)

I think it's a gross misrepresentation to say that the customer is always best off booking directly with the hotel. You get something you wouldn't get when booking directly through the hotel.

When you use an OTA you have collective bargaining power; If the hotel screws you around in any way it's now the OTA's problem. They'll call up the hotel on your behalf (in their native language, which you may or may not speak) and either sort it out with them or make sure you have somewhere else to stay because you're now their customer.

Of course the service you get differs a lot by OTA. But from the customer's perspective there's usually a net gain by booking through one.