I could make a list several hundred items long, but I'll just start with a few and see if anyone else wants to join in.
You've been on Ravencrest too long if...
... you know where the name "Ravenfail" came from and who first coined the phrase.
... you miss forum posts by Zephro, Dethricar, Padook, Alma, or Triv.
... you remember Sophiedoll and know Camirex, Landpwnian, and Dringet would have put him (or her) out of business.
... you know why Gudwin = Kenny.
... you remember the time Requiem got hacked (oh noes!)
... you know why "would rather be fishing" and "snuggle" are awesome.
... you miss the good ole days of guild drama that brought our server a little infamy in the pages of WoW Insider.
... you rolled an alliance character just so you could try to kill Chaney.
... you rolled a horde character just so you could try to kill... er... what is world pvp again?
... you gave up trying to catch up with Raziya's pet collection a LONG time ago.
... you can list 4 people whose boss fight explanations in PUGs last longer than a high school graduation ceremony.
... there are a LOT of awesome players you miss gaming with and hope they come back for MoP.