Gilbert Arenas lost his bid to keep his ex-girlfriend/fiance from appearing on the show Basketball Wives (a misnomer of a reality show as all the participants are ex-wives or ex-girlfriends of b-ball players). One of his arguments in asking for the injunction was the invasion of his privacy that would occur if the ex were allowed on the show to complain about him. The judge found that this claim was so much noise signifying nothing. Specifically, Arenas has a twitter account -- with allegedly thousands of followers -- from which he tweets constantly about his personal life. In other words, you can't claim your personal life is personal if you splash it all over the internet.
Newsflash: the internet is not private.
Everything you post on the internet is public. Someone somewhere will see it. Even if you have "privacy" settings, do the people who have access to your "private" account also have privacy settings? Do their friends? And so on and so on and so on. If you post it, they will see it.
This is true for celebrities with thousands of twitter followers and true for folks with all of 5 friends on Facebook. Let me repeat: the internet is not private.
If you are going through a custody/divorce/child support, do not post on facebook, twitter, google+ or anyplace on the internet anything about your ex. Just don't. Smart attorneys (like me) will get that information and use it against you. The judge won't buy your argument of "I was just venting, I didn't think anyone would see it."
Besides, do you want your kids to see what you posted about the other parent or have their friends see it? It doesn't help the situation, can only hurt it, so just don't do it. Resist the temptation to "get even."
If you have been so foolish as to do post all over the internet what a jerkface your ex is, do not then try to remove it. You can bet your last pleading that someone already screen captured the posting and sent it to your ex. Who then helpfully forwarded it to the lawyer. Now, they can bring up something called "spoliation of evidence" meaning you destroyed possible evidence in the case. This is a very bad thing to have happen.
One last thing about the internet, do not friend your ex, or have your friends do so for you just to gather incriminating evidence. Yeah, it sounds like a good idea. In practice it 1) doesn't help things at all and 2) just makes you look petty and vindicative in court. As an attorney, I really try to avoid having my clients look petty and vindicative.
In short -- SHUT THE HELL UP. It will help your case much better than any posting anywhere on the internet you can make.