Yeah, really... The only people I can see complaining about a system that brings guilds closer together and gives them one more thing to work together on would be the sort of person that rubs EVERYONE the wrong way due to thier crappy personality and is constantly getting kicked out of guilds.
Another poster had it right, this change is FANTASTIC for the game in general. Fewer guilds in which people will actually want to be in and being better people in general as to not have to start all over again and gain rep in another guild to get their perks. A server with 30 or so max level guilds with 500+ people would be so much better then a server with 500 guilds with stupid guild tags running around making people's lives that much more difficult.