For one, the EU server of Blade's Edge, has a strange habit to promote the use of PvP gear, in PvE playing. I have written about this before and I still cannot understand where that comes from, but they do it a lot. It was never an odd sight to go into a heroic dungeon, have a look at your fellow gamers' gear and see just stacks of useless PvP gear.
On the Aerie Peak server, the current realm that I occupy, has shown me another extremely strange habit; the PuG demanding to show your achievements before you can join up, and today reading on wow.com I realized this is not just an Aerie Peak quirk, but a habit that spans a lot of different servers.
The authors at wow.com, and the subsequent bloggers that they read upon, are just as baffled by this rediculous trend as I am. What they demand is that, e.g. to join a Naxx10 group, you have to link your [Epic] or [Fall of Naxxramas] achievements. The same is for even stupidly easy raids like Vault of Archavon. In essence, you are asking that you only want people who are stupidly outgeared for the instance, in hopes for a quick and smooth run.
This sort of behaviour only truly makes sense if you are PuG'ing particularly difficult encounters, like Emalon or Sartharion with drakes on board. In fact, it is a sound theory that this is where it all started from, but has since grown out of control. Monkey see, monkey do, usually only leading to its own downfall because any experienced player (with a head to draw sense from) knows that achievements can be completed and epics acquired, without actually having any skill.
And skill is the key. I have witnessed, time and time again that the people you want on your side, are the people who can get really good results, even in the worst gear. Completing Naxxramas in blue gear, enduring obstacles and performing against all odds, can only be accomplished by having the skill to play. Yes, achievements and gear are good indicators towards it, but are far from reliable.
All you, really, end up doing is recycling the same dirty laundry, since you are recruiting people with the achievements and/or gear over those without it, ending up with the same bad apples as last time, and the time before that. How many times do you see people die on silly mistakes, doing e.g. Heigan or Thaddius? The answer is, everytime, whether they have completed it before or not.