Our happy hour fact to amaze your drinking buddies with.

The social networking site Facebook appears in one in five divorce petitions filed this year.

Divorce-Online, a Web clearinghouse for legal information on divorce, did a keyword search of 5,000 divorce filings in their 2009 database and found that 989 contained the word "Facebook." The majority of these citations concerned one involved party using the site for inappropriate sexual chats with someone outside of his or her marriage.

Social networking sites like MySpace and Twitter were also mentioned in their fair share of filings, but Facebook popped up more frequently. Web flirters should be warned that these days divorce lawyers spend a lot of time searching the Internet for signs of infidelity.

With the changes to Facebook's privacy settings offering users more opportunities to be tempted by sexy strangers, the institution of marriage may struggle to survive 2010.