Returning from a long WoW break always brings some novelties. I can now buy a flying mount for my level 60 warrior! My warrior gets Shield Slam for free! And everywhere I look I see "Need one member for instance X, minimum gearscore 2800, link achievement". It seems like everyone has been brought back to a single number. The e-peen meter promised by Blizzard two weeks ago doesn't seem so funny any more.
Out of curiosity I checked the gearscore meter of my stabled Death Knight. She ran Naxxramas until she had everything she needed. Yet I saw people looking for members for their Naxx run with a gear score above mine. Why would someone who doesn't need a single item from Naxx anymore still want to run it? The people who do want to raid Naxx will be those who have gear from heroics, not people who are doing Icecrown Citadel.
Looking at the past, the gearscore does feel like a natural evolution. Everyone wants to run a fast instance without wipes. If you only instance with guildies you don't have a problem. But how do you know if that pug mage is any good? In the vanilla WoW days you would just try them out and add them as a friend if they were good. Soon enough you'd have a list of good players. With the introduction of achievements we found another way. Link the achievement to show us that you already finished the instance once! And the newest trick would be to link your gearscore.
All these tricks are of course flawed. How can you be sure that imba-geared mage really is any good? Did she just run a few instances auto following her friends? And maybe that guy who got the achievement just ran behind all the rest and leeched his victory. You can't be sure but your chances of success should go up.
Where will this evolution end? Shall we keep a huge hall of shame database like Tobold suggests? I can imagine a huge ranking system. Every time you walk in the fire or do pathetic DPS for your gear level your ranking goes down. Killing more and harder bosses will let you rise on the ladder. And for the very top of the chain you'd have to kill Arthas naked... with five men. Then again that top hundred player probably won't be interested in running your Naxx run.