Social media sites like Facebook might be fun, but if you have a legal case, beware of discussing it or anything that might be a case issue there. Your seemingly innocent but potentially damaging statements might find their way to your legal opponent through others. But the greater and more realistic fear is that your statements, which can be used against you in court, will be the focus of formal discovery proceedings.
For example, in personal injury cases, it is common for my injured clients to be asked during deposition if they have a Facebook or Twitter account. If they do, the defense lawyer then is able to ask for information which opens up that account for a search for discussions about things the client said on social media about accident details and how bad his injuries are. Using social media, people usually don't take the time to give absolutely accurate information, so what is said there could conflict with later deposition testimony. That causes big problems in a legal case.
Here's a real example. During a deposition, the person who was hurt said he can't fish because the rocking of a boat hurts his injured back. Obviously, on a given day, he might feel pretty good, go out fishing just one time in 8 months, and brag on Facebook about the fish he caught. The insurance defense lawyer then uses that one posting to paint the injured person as a liar.
In another example, a couple on a motorcycle was struck by a car. The car's driver had posted on his Facebook page a photo of his prized car with a caption that read, "Ready to drive at 90 mph." The injured couple's attorney is using that statement, probably made in an unthinking moment, as evidence against the car's driver.
Every case of whatever kind has the risk of being damaged by social media messages, so if you are about to be or are involved in a legal case, silence is golden.