Private and public data aggregators (such as http://www.peekyou.com, http://www.instantpeoplefinder.com, http://www.ussearch.com) make access to personally identifiable data such as address, telephone, possible relatives, date of birth, maiden name, property information, email addresses, and other data as easy as typing the name in a search engine and paying a small fee.
This data can be then used for criminal activities such as identity theft and social engineering. It is also often used by stalkers. The ways this data can be maliciously used or otherwise misused are numerous. Also, regardless of how the data is used, people should have the right to not have their personally identified information to be accessed so easily. Opt-out requests are ineffective for limiting such access.