When you give personalized information to a website, it's often with the understanding that the site will give you a higher-quality service in exchange. But many websites do the reverse: they gather your personal information and use it to calculate how much more to charge you based on your profile — they invade your privacy and charge you more to boot:
CNN has a report detailing an unsavory practice euphemistically called "price customization." In short, websites examine the web data you automatically shed (cookies, IP address, etc.) so they can charge you a different price for a product or service depending on your "identity" and shopping habits.
The article cites "a retail photography Web site charging different prices for the same digital cameras and related equipment depending on whether shoppers had previously visited popular price-comparison sites" and "one [Amazon] buyer [who] deleted the electronic tags on his computer that identified him as a regular customer and noticed the price of a DVD changed from $26.24 to $22.74."
