Some friends of mine in game have recently had the experience of having the rug pulled out from under them: their 25 man raiding guild, for whatever reason (I'm only privy to one side) has decided to go 10 man strict, leaving 15 or so people out in the cold. So now, this late in the expansion, they're forced to either seek new homes or try and start something up for themselves.
It's really hard to watch good people suddenly find themselves lacking that role they'd grown accustomed to and not really be able to do much of anything. I've been there myself back at the end of Vanilla, as a move and real life commitments took me away from the game for four months, and by the time I returned everyone had moved on. It's hard to feel like you don't have a place in game anymore, as WoW is such a social experience. At least now there's the Dungeon Finder and raid PuG's that didn't exist before, and most of them are geared enough that they'll find a home eventually, but it still seems so discouraging to be in the position of trying to get back to where you were while everyone else moves forward.
So now it falls to you to tell inspiring tales of overcoming a similar difficulty or share your tales of guild breakups and recoveries.