Issues

Privacy concerns with social networking services have been raised growing concerns amongst users on the dangers of giving out too much personal information and the threat of sexual predators. Users of these services also need to be aware of data theft or viruses. However, large services, such as MySpace and Netlog, often work with law enforcement to try to prevent such incidents.^{[citation needed]}
In addition, there is a perceived privacy threat in relation to placing too much personal information in the hands of large corporations or governmental bodies, allowing a profile to be produced on an individual's behavior on which decisions, detrimental to an individual, may be taken.
Furthermore, there is an issue over the control of data—information that was altered or removed by the user may in fact be retained and/or passed to 3rd parties. This danger was highlighted when the controversial social networking site Quechup harvested e-mail addresses from users' e-mail accounts for use in a spamming operation.
In medical and scientific research, asking subjects for information about their behaviors is normally strictly scrutinized by institutional review boards, for example, to ensure that adolescents and their parents have informed consent. It is not clear whether the same rules apply to researchers who collect data from social networking sites. These sites often contain a great deal of data that is hard to obtain via traditional means. Even though the data are public, republishing it in a research paper might be considered invasion of privacy.^[3
Privacy on social networking sites can be undermined by many factors. For example, users may disclose personal information, sites may not take adequate steps to protect user privacy, and third parties frequently use information posted on social networks for a variety of purposes. "For the Net generation, social networking sites have become the preferred forum for social interactions, from posturing and role playing to simply sounding off. However, because such forums are relatively easy to access, posted content can be reviewed by anyone with an interest in the users' personal information".
Following plans by the UK government to monitor traffic on social networks schemes similar to E-mail jamming have been proposed for networks such as Twitter and Facebook. These would involve "friending" and "following" large numbers of random people to thwart attempts at network analysis.