Update: the "1 in 5 divorces in the US" statistic is from December 2009 and has simply been pushed to the top again by a new press release. All the other statistics in the original story (below) are new:

Facebook is cited in 1 out of every 5 divorces in the United States, according to the Loyola University Health System. Furthermore, 81 percent of the country's top divorce attorneys say they have seen an increase in the number of cases using social networking evidence during the past five years, according to a recent survey by the American Academy of Matrimonial Lawyers (AAML). Last but not least, Facebook is the unrivaled leader for online divorce evidence with 66 percent citing it as the primary source, the AAML said.

It's not that Facebook is solely to blame: already-strained marriages are bound to break with or without the service. Still, a couple doesn't have to be experiencing marital difficulties for an online relationship to develop from mere online chatting into a full-fledged affair.

In the end, Facebook is a social tool. For single people, social networks can help them meet that special someone. Even for marriages, social networks can help further along a relationship. Just like with any other social medium, however, even the most innocent of intentions can turn ugly with improper use.

You don't need to be a psychologist to realize that Facebook can accelerate the process. Stories of people whose marriages were destroyed by affairs that began on social networks abound on the Internet.

Remind yourself why you're using a given service and regularly assess your intentions with the people you're frequently communicating with. Facebook may not call itself a dating website, but hundreds of millions use it to connect on varying levels. Intimate conversations, even online ones, should only be reserved for your significant other.

"We're coming across it more and more," licensed clinical psychologist Steven Kimmons, PhD, of Loyola University Medical Center in Maywood, Illinois, said in a statement. "One spouse connects online with someone they knew from high school. The person is emotionally available and they start communicating through Facebook. Within a short amount of time, the sharing of personal stories can lead to a deepened sense of intimacy, which in turn can point the couple in the direction of physical contact. I don't think these people typically set out to have affairs. A lot of it is curiosity. They see an old friend or someone they dated and decide to say 'hello' and catch up on where that person is and how they're doing."