High Quality Content by WIKIPEDIA articles! Social networking sites greatly vary in the levels of privacy offered or even required. With some sites, such as Facebook, the use of real names and uploading of personal information is encouraged (onto a page known as a ‘Profile‘). This may include birthday, address, telephone number, and more intimate details such as interests, hobbies, favorite books/films/music, relationship status. There are others, such as Match.com, where the use is designed to encourage anonymity, and thus linking users to individuals can be difficult. However, even with sites that discourage the use of real names, individuals can be identified, such as through face re-identification. It has been estimated by studying two major social networking sites that a 15% overlap of the same or similar photographs makes it possible to identify profiles with similar pictures on other sites. With sites that do encourage information disclosure, it has been noticed that the majority users seem happy to disclose as much information as possible and to as many people as possible. In 2005, a study was performed in which data was analysed from 5, 540 Facebook profiles from students at Carnegie Mellon University. It was revealed that 89% gave a name that was likely to be genuine, and 61% gave a photograph suitable for direct identification. The visibility of this personal information is highly variable. The vast majority of users also had not altered their privacy setting, enabling a large number of presumably unknown users to have access to their displayed personal information (the default setting originally allowed friends, friends of friends, and non friends of the same network to have full view of a user‘s profile). It is possible for a user to block other users from seeing their presence on Facebook, but this must be done on an individual by individual basis, and would therefore appear not to be commonly used for a wide number of people. All of this has led to many concerns that users are displaying far too much information on social networking sites which may have serious implications on their privacy. Facebook has especially been criticised due to the perceived laxity regarding privacy in the default setting for users, which evidence suggests most do not alter. The reason social network security and privacy lapses exist results simply from the astronomical amounts of information the sites process each and every day that end up making it that much easier to exploit a single flaw in the system. Features that invite user participation—messages, invitations, photos, open platform applications, etc. -- are often the avenues used to gain access to private information, especially in the case of Facebook. Adrienne Felt, a Ph.D. candidate at Berkeley, made small headlines last year when she exposed a potentially devastating hole in the framework of Facebook`s third-party application programming interface (API) which allows for easy theft of private information. Felt and her co-researchers found that third-party platform applications for Facebook gave developers access to far more information (addresses, pictures, interests, etc.) than needed to run the app. This potential privacy breach is actually built into the systematic framework of Facebook, and unfortunately the flaw renders the system almost indefensible. "The question for social networks is resolving the difference between mistakes in implementation and what the design of the application platform is intended to allow," David Evans, Assistant Professor of Computer Science at the University of Virginia, says. There`s also the question of whom we should hold responsible for the over-sharing of user data? That resolution isn`t likely to come anytime soon, says Evans, because a new, more regulated API would require Facebook "to break a lot of applications, and a lot of companies are trying to make money off applications now." Felt agrees, noting that now "there are marketing businesses built on top of the idea that third parties can get access to data on Facebook."