Before they tie the knot, a growing number of couples are signing on the dotted line. But they're not signing financial prenuptial agreements. Instead a growing number of couples are agreeing to social media prenups.

"It's a gold mine of information," said Atlanta family attorney Rebecca Crumrine Rieder, who says the law is just catching up with social media. It's a treasure trove of dirt during a trial or a nasty divorce. Now we know it's also a leading cause.

The American Academy of Matrimonial Lawyers says 80% of divorcing couples cite social media as a reason for their breakups.

It's why attorneys are now preparing prenuptial social media agreements.

"Your public persona is so important to how you're going to be able to handle your business," Rieder said.

So, what's in a social media prenup?

It would include a definition about what you and your spouse agree is allowed. It could be no posts about the other person unless permission is given. It covers video, photos, and comments. Rieder points out it doesn't matter if they're true or not.

The prenup also needs to include specific dates: will it apply while you're married, or only if you file for divorce?

And of course, there's the part that makes it all work: the costs for each violation.

"You're going to catch something that you or your spouse say in anger or revenge that you're going to regret later, or it's going to hit your pocketbook," Reider said.