I've always considered a Facebook unfriending to be tantamount to nuclear attack, i.e. a foray into a new era from which there is no turning back. The Rubicon has been crossed and, even if you re-friend the person, the damage has been done and the trust is gone. While there's no problem with someone quitting Facebook, or cutting their friend base down to only the people they know in real life, unfriending an actual friend… well thems fightin' clicks.
Per the St. Petersburg Times, a woman in Brooksville, Florida unfriended her live-in boyfriend whilst in a pique about something or other. And that very umbrage came back manyfold as the live-in boyfriend confronted his lady about both the unfriending and her status change to single (and, implicitly, ready to mingle). Eventually, the fracas came to such a boil that Johnny Law was called to the feuding couple's mutual residence. They both claimed that the other had started the physical violence, but neither could deny that the young woman had unfriended her guy. Top 10 Facebook Etiquette Rules
While whatever level of physicality that led to the fuzz getting called is unacceptable at any level, we should all take heed not to unfriend or status change a likely unstable, cohabiting lover and/or Floridian. Some people take their Facebook friendships very seriously, and you wouldn't want to end up on an (admittedly potentially phenomenal) episode of Cops.
Hopefully, you're classy enough not to unfriend your fellow cohabitor, or change your status without talking things over with your partner. Facebook Manners And You