Privacy on the Internet is… well, let's just say it's complicated. This article, analyze a few open source tools and concepts that might be used to increase privacy on the Internet for yourself. Some of the tips you will find useful, others you will discard, and still others you might use in conjunction with other policies to construct your own privacy model.
The concept of privacy is a difficult thing to pin down. It gets muddled up with other big ideas, like anonymity and secrecy and even criminal activity. Whatever "privacy" means to you and whatever you might associate it with, most people agree that we have a right to it, if not necessarily online or in public, then at least on some level.
That means that some portion of our computing life should also have the privilege of being private. How far that extends differs from one person to another. For one person, an implied guarantee of privacy is sufficient (a website wouldn't require a password if it didn't intend to keep user data private, right?), whereas another might prefer to use aliases for online interactions and nameless spending accounts that cannot be traced back to the real world.
Another thing that differs from one person to another is the price they are willing to personally "pay" for privacy. It's a balancing act, after all. Is "mostly" private good enough for you? Or are you willing to invest more time and effort into ensuring that your information and information about you is concealed no matter what?