Facebook pages should not be immune from the rules governing discovery. They should be treated like personal journals or diaries. This does not mean that in every case a defendant will be entitled to read the plaintiff's Facebook page. That is not how the law operates.
Much like in the context of a diary, defendant's counsel should use the opportunity of examinations for discovery to determine if it is likely that the plaintiff's Facebook page contains relevant information. Counsel should inquire whether the plaintiff posts status updates or photographs, how many ‘friends' they have, and how often they access Facebook. If plaintiff's counsel has not reviewed their client's Facebook page, it is appropriate to request an undertaking that they do so and that they produce an updated Affidavit of Documents disclosing any relevant information.
Facebook pages are best thought of like a box full of diverse documents that may or may not be relevant to the allegations in a claim. Those that are relevant must be disclosed. If a plaintiff makes a post or uploads a photo on Facebook that contradicts their evidence, it is important that the defendant be able to seek its production.
Unfortunately, there is a good deal of confusion when it comes to Facebook pages. Some defence counsel seek production of the entire Facebook page and move before the court to compel access to the page. Naturally, the courts resist this sort of intrusion.
In its analysis, the court will consider the likelihood of relevant information on the page. One example would be if there are photographs of the plaintiff engaging in activities that she says she is unable to perform as a result of her injuries. In coming to a conclusion, the court will also consider the plaintiff's expectation of privacy. If the plaintiff has a large number of friends and intends that their posts be public, the court is more likely to allow production.