It's Complicated?

On Facebook & many other sites there is a wide variety of relationship status options one can pick from to list on their profile. Facebook gives the following choices:

• Single
• In a Relationship
• Engaged
• Married
• It's Complicated
• In an Open Relationship

When it comes to relationship status, I am curious what "It's Complicated" means. As far as I know, you're either in a relationship or not.

Is this a choice for those actually in a relationship but still want to keep their options open? Maybe it's for divorsed couples who still live together to make ends meet. Why not just say you're single or in an open relationship? And why would someone want to hookup with someone who is in a complicated point in their life?

Can someone please share a good reason for selecting the "It's Complicated" relationship status?

UPDATE: Poll Results 1/20/09 - 1/27/09

Do you have a good understanding of the "It's Complicated"
relationship status?
40% I have first hand experience
00% I understand what it means
60% I don't get it
00% Meh