A few weeks ago, I got tickets for Cirque du Soleil's Love show at the Mirage for a date several months in the future. I decided to stay at the Mirage, and found what I thought was a good deal for $99/room. I strongly suggested to my wife that we book the rooms, but she said it was late at night and she wanted to research other hotels the next day. She said there's no way the rates would go up over night.
So the next morning, I checked the rates again online, and to my surprise the rates had increased to $119. My wife was shocked that they would go up so quickly overnight in the middle of the week, considering our reservation was for several months away.
I have worked in information security for many years, so I was quite suspicious about this overnight rate increase. To confirm my suspicions, I used a different web browser on the same computer, and I used another computer in my household with the original web browser. In both cases, I was offered the lower $99 rate that I got the night before.
I then called the central reservations number and told them about the differing rates. I waited on hold while the reservations agent spoke to a supervisor. She did not give me an explanation for the rate differences, but she said she would honor the lower rate.
This practice can only be explained by what I consider an unscrupulous use of tracking cookies. The first time you visit the online reservations, it leaves a little piece of information (a "cookie") on my computer which is linked to the price quoted in the MGM Mirage reservations system. When I re-visited the site the next day, it used the cookie to retrieve the previous price quoted, and then the reservation system increases the price by a certain percentage or dollar amount. When I used a different browser or a different computer, this cookie did not exist, and so it gave the lower price for first-time visitors.
Whether this is a form of illegal price discrimination is up to the state's attorney general and the FTC to decide. At the very least, they are preying on consumer's emotions to make an irrational decision based on the perception of increasing prices or increasing demand.