The prolonged confinement of a would-be 'friend' on a social networking website to a 'friend request' page. Results from never denying or accepting the prospective friend's offer to become friends. Often appears when a member has forgotten the prospective friend from some previous experience, or a member has never met the prospective friend, resulting in a dilemma for the member, who does not want to accept the friend, but wants to avoid hurting the friend by rejecting them.
NOTE: 'Friend limbo' cannot be modified by a possessive pronoun; one cannot be 'stuck in his friend limbo' or 'be keeping many people in one's friend limbo.' Friend limbo is non-specific, like 'Davy Jones' Locker.' Just as one cannot be stuck in someone's Davy Jones' Locker, one cannot be stuck in someone's friend limbo.
To put or leave someone in friend limbo.
Damn, Jebediah, don't you remember me? We were roommates three years ago, but you haven't 'friended' me - I'm still stuck in friend limbo!