Yet when a court wants to use material from a social networking page in a case there is a web-wide sharp intake of breath.
There are objections to the use of this material and shock that this use is even possible at all.
It is an odd reaction because there is no reason why information published on social media sites should be especially private. If a court can demand that it see and use a private letter, or hear details of a private conversation, it is perfectly natural that it be able to demand to see what you post on your Facebook page.
Perhaps it is to do with the word 'private'. Maybe users think that this locks information off from the world. That is true, up to a point, but it can't hide it from the legitimately prying eyes of the court.
What, exactly, are the court's rules, then? With exceptions for communications with a lawyer a court can demand to see private material – including letters, emails, diaries – if it is relevant to the case. The litigation rules in England and Wales, the Civil Procedure Rules, broadly define "documents", meaning that electronic documents which can be demanded can include instant messages and content from social networking sites.
This is becoming an increasingly common feature of court cases. Rane Zimmerman was a forklift driver at a warehouse owned by Weis Markets in Pennsylvania in the US. He said that he hurt his leg at work and claimed damages for lost wages.
Weis Markets said that they thought his Facebook and MySpace pages indicated that his leg was not as damaged as he claimed and asked the court to give it his passwords for those pages so they could check.
It is entirely reasonable for the court to order that information from these social media platforms be allowed in court if it is relevant. The information is private, up to a point, but if a court decides it is important in deciding the facts of a case, it should be possible to examine it.
What will rightly give some observers cause for concern is that the court agreed to demand the handing over of Zimmerman's usernames and passwords.
This will give his ex-employer access to far more private information than just that which is relevant to the case and is a mistake.
Rather than one side being handed access to all this private information, the material in question should just form part of the normal bartering that goes on before a case between lawyers that determine what will and will not be admitted as evidence. That information appears on a social media page rather than in an email or in a diary should not change its value as evidence at all.
Social media sites give an insight into people's lives, just as written letters used to and diaries still do. Anyone who is thinking of going to court should first think about what others now know about them through this medium. Can their claim be supported? Or has it already been undermined on countless acquaintances' computer screens around the world?
This material is fair game as long as courts respect the normal processes of evidence gathering, and users of these platforms will just have to get used to the accountability that comes with their private lives being that little bit more public than before.
Claire McCracken is a technology law specialist with Pinsent Masons, the law firm behind OUT-LAW.COM.