Who are "they?"

You always hear about "them".  "They" say not to swim 30 minutes after eating, or "They" say celery is a negative-calorie food.  Who are "they?" 

Today I was watching a DVRed Dr. Phil (yes, I'm a Dr. Phil phan), which was about sibling abuse.  The statistic that alarmed me was that "they" say 53 out of 100 siblings report that they experienced sibling abuse.  Really?  Again, who are "they"?  Really?  That is more than spousal abuse and child abuse statistics.  And what constitutes "sibling abuse"?  Could it possibly be that "abuse" is defined as both children tormenting each other as all siblings do?  Am I possibly guilty of this so-called abuse?  I would venture to guess that every child who has a sibling is guilty of it.  For example, my brother used to drive me CRAZY (I suspect just to get a rise out of me, then laugh at me).  He used to hold me down and see if he could suspend spit from his mouth until it was mere inches from my face before he sucked it back up.  By the way, that is so gross.  I am sure I "abused" him at some point too, although he was bigger than me for the majority of our childhood, so any pain I inflicted on him was immediately reciprocated.

I guess I should start making of list of things I did wrong to Alex.  Then I guess we should find a therapist and work through our 'issues' together before they affect other areas of our lives.  Whatever.  That is the biggest load of manure I've ever heard.  I would put my money on it that "they" are mad at their older sibling for putting them through rites of passage that every sibling goes through (spit test included).