Privacy concerns exist wherever personally identifiable information is collected and stored - in digital form or otherwise. Improper or non-existent disclosure control can be the root cause for privacy issues. Data privacy issues can arise in response to information from a wide range of sources, such as:

The challenge in data privacy is to share data while protecting personally identifiable information. The fields of data security and information security design and utilize software, hardware and human resources to address this issue.

Various types of personal information often come under privacy concerns.

The ability to control what information one reveals about oneself over the Internet, and who can access that information, has become a growing concern. These concerns include whether email can be stored or read by third parties without consent, or whether third parties can track the web sites someone has visited. Another concern is whether web sites which are visited collect, store, and possibly share personally identifiable information about users.

The advent of various search engines and the use of data mining created a capability for data about individuals to be collected and combined from a wide variety of sources very easily. The FTC has provided a set of guidelines that represent widely-accepted concepts concerning fair information practices in an electronic marketplace called the Fair Information Practice Principles.

In order not to give away too much personal information, e-mails should be encrypted and browsing of webpages as well as other online activities should be done traceless via anonymizers, or, in cases those are not trusted, by open source distributed anonymizers, so called mix nets, such as I2P - The Anonymous Network or tor.

A person may not wish for their medical records to be revealed to others. This may be because they have concern that it might affect their insurance coverages or employment. Or it may be because they would not wish for others to know about medical or psychological conditions or treatments which would be embarrassing. Revealing medical data could also reveal other details about one's personal life (such as about one's sexual activity for example).

Physicians and psychiatrists in many cultures and countries have standards for doctor-patient relationships which include maintaining confidentiality. In some cases the physician-patient privilege is legally protected. These practices are in place to protect the dignity of patients, and to ensure that patients will feel free to reveal complete and accurate information required for them to receive the correct treatment.

Information about a person's financial transactions, including the amount of assets, positions held in stocks or funds, outstanding debts, and purchases can be sensitive. If criminals gain access to information such as a person's accounts or credit card numbers, that person could become the victim of fraud or identity theft. Information about a person's purchases can reveal a great deal about that person's history, such as places he/she has visited, whom he/she has contacted with, products he/she has used, his/her activities and habits, or medications he/she has used. In some cases corporations might wish to use this information to target individuals with marketing customized towards those individual's personal preferences, something which that person may or may not approve of.

Political privacy has been a concern since voting systems emerged in ancient times. The secret ballot is the simplest and most widespread measure to ensure that political views are not known to anyone other than the voter themself—it is nearly universal in modern democracy, and considered to be a basic right of citizenship. In fact even where other rights of privacy do not exist, this type of privacy very often does. The United States has laws governing privacy of private health information, see HIPAA and the HITECH Act.