Surveillance cameras, tax reporting, Internet-based data, emails, mobile phone records and their cameras are some of the more salient modern ways that provide information on individuals and organizations. Few object when banks and other organizations use surveillance cameras on their premises to deter theft and robbery. There is much greater concern when Internet companies like Google and Facebook use their vast stores of data to learn about the interests and other personal information, of the millions of individuals who use their services. Probably, however, the most serious threat is the misuse of “big data” by governments, including democratic governments.

This past week the possible misuse of extensive data by the Internal Revenue Service and the Justice Department has been widely reported. Prior to the presidential election in 2012, tax inspectors may have singled out for closer scrutiny the applications of “Tea Party” and other conservative organizations for tax-exempt status. The Justice Department secured telephone records of reporters for the Associated Press in order to find their sources for leaked information. Data mining with advanced technologies played a part in both alleged abuses of governmental power.

To be sure, using the vast data resources of modern governments to target opponents is not new. For example, Richard Nixon wanted tax inspectors to audit his list of “enemies” and avoid auditing his friends, but George Shultz, the then Secretary of Treasury, refused to go along. What is different now is the explosive growth in governmental (and private) access to “big data” with extensive information on millions of individuals and hundreds of thousands of organizations.

Of course, big data has many valuable uses. To give a few examples, health insurance companies can better forecast their future financial obligations from their extensive information on the past health, use of medical resources, and other behavior of millions of insured individuals and families. Economists use the vast government social security data to track how earnings of different individuals vary over the lifecycle, and even how the earnings of children are related to those of their parents. Governments use their extensive information on incomes and deductions to discover who is likely to be underreporting their incomes and over reporting their deductions to tax authorities.

Yet each of these and other big data sets is subject to abuse. Extensive health histories enable insurance companies, unless checked, to reclassify men and women into worse health categories as they age and experience health problems. Such reclassification takes away the prospect of individuals getting some long term health insurance from annual insurance contracts. Big data sets available to researchers have been manipulated to identify individuals and corporations. Already mentioned is that governments sometimes use extensive tax information to target individuals and groups who oppose them. The information from government surveillance cameras, as Posner indicates, may be improperly used for political advantage, as when cameras detect well-known political leaders in cars with women who are not their spouses.

Fortunately, the Internet, social media, and other modern technologies are not only a major source of the big data that is sometimes used for bad purposes, but these technologies often also help expose these abuses. Individuals who become privy to damaging information about governmental (or private) behavior can publicize that behavior on the Internet to vast audiences. For example, since information about these events is quickly posted online,The Internet has forced China to admit to events that in the past would have been kept secret, such as governmental land grabs, protests against local pollution levels, local health epidemics, and deaths from mining disasters,

How to harness big data to socially valuable purposes while keeping down abuses is becoming an important priority in democratic societies. The Internet is an important source of big data, but it also is an increasingly valuable way to control the abuses.