And let's not forget the personalized pricing some companies are doing. They read your "cookie" and know who you are, so they adjust their pricing accordingly.

If you always buy a particular trip (like I do), they may well decide you'll sit still for a higher price than the next guy.

It's insidious, and it's coming under some heat and investigation, but it's real. I just don't know if NW practices it. One way to find out is to do identical searches, one from your own computer (where they have the cookie) and another from a different computer. If you notice lower prices on the anonymous computer, they've got your number!