Sometimes people may want to do things anonymously. For example, a rock star buying a beach house might want to avoid unwanted attention from neighbors, or someone posting to a dating list might want to view replies before making a date.
Deirdre Mulligan [MUL99] lists several reasons why people might prefer anonymous activity on the web. She explains that some people like web anonymity because it reduces fears of discrimination. Fairness in housing, employment, and association are easier to ensure when the basis for potential discrimination is hidden. Also, people researching what they consider a private matter, such as a health issue or sexual orientation, may be more likely to seek information first from what they consider an anonymous source, turning to a human when they have found out more about their situation.
Anonymity, while having benefits, can also create problems. If you are trying to be anonymous, how do you pay for something? You might use a trusted third party (for example, a real estate agent or a lawyer) to complete the sale and preserve your anonymity. But then the third party knows who you are. David Chaum [CHA81, CHA82, CHA85] studied this problem and devised a set of protocols by which such payments could occur without revealing the buyer to the seller.