When nothing has happened on Facebook since your last login. Facebook drought can make you feel sad, because it makes you realize that you've logged in 5 times within the last 2 hours. This shows that, for the moment, you don't have much of a life at all.
Person 1: Stop bothering me, go away and do something.
Person 2: Sorry...Facebook drought.
Person 1: You're ok? You seem a bit down today?
Person 2: I'm fine...it's just...Facebook drought.
Person 1: Oh...I'm sorry, man. I didn't know...