For years airlines have been using internet browsing history and cookies to view which customers have previously searched for similar flights and raised their prices on the fly.
This is a breach of privacy, a misuse of internet technology and harmful to the consumer.
In order to get the lowest price, consumers are forced to use special browsers (like Chrome's incognito mode) or clear their history and cookies to avoid paying arbitrary increases in ticket prices.
Here is a 2013 article from USA Today about the practice: http://www.usatoday.com/story/travel/columnist/seaney/2013/04/30/airfare...