This. This is the single event in my mind that significantly changed the average players outlook on the game. The honor system is the second. World PVP and BGs prior to the honor system (even after to some extent, but prior to cross-realm) were the most fun in the game. Guild vs Guild to prove who was the best. No one surrendered flags to end the game cause it is more points/hour to lose fast than win slow or any of that crap. You were there for the long haul and there to win. Also, the amount of dickbags was much lower due to the fact that if you pissed off your realm enough you couldn't meaningfully play. Now you just do whatever you want, act like an ass 24/7 BG or 5man and who cares? There are 4 other idiots you've never met before that will be more than happy to deal with your bullshit after waiting 45minutes for a tank.
At the end of wrath I hardly knew what guilds on my realm on my faction were good let alone what guilds on the other faction were. Who cares? You don't really have to interact with anyone on your own realm.
Accidentally posted as AC
Memory fault -- brain fried