ArenaNet hid these large kites all over the map and gave the players points for finding them. Six out of seven of these kites are in the PvE (player versus environment) area that is created to be completed cooperatively with other players. The one remaining kite is hidden in WvW (world versus world) area that is created for servers with real players to battle each other. I am guessing, but it seems the developers of the games put a major objective in the competitive environment so players who don't normally go into that area are forced to venture into the dangerous lands of WvW.
The developers make the game and can intend whatever they want, but the consumer of the product (the players) have quite a lot of control over what happens with that content once its released. In this case, the players could chose to play the game as it was meant to played and fight for control over the kite or they could choose to stop fighting in WvW so that everybody could get the achievement. I'm interested in what actually happened. I'm not sure if it's sociology, psychology, or something else that deals with crowd dynamics, but I'm sure plenty of people would have had fun studying the result when ArenaNet put an important achievement atop a hill and allowed players to kill for it with little consequence. The result was different on separate servers and varied slightly over time, but I can report my experience even if I didn't stand around for days with a clipboard recording interactions.
I was completing this with my guild. They were talking me through the whole thing and teleporting me past the hardest parts of the puzzle. I found that I could run around that area and not get attacked at all as long as I stayed largely out of the way. My guildees told me others weren't so lucky. What ended up happening where I was playing was that people were safe or unsafe based on their guild. People kept track of the major guilds on each server and whether they were being friendly or unfriendly toward people who were trying to get their achievement. My guild is full of kind, cooperative adults so for the most part we ran around unhassled in a part of the game that would normally have been a death trap. It reminded me that it's really important who you associate with. A lot of guilds were being killed on the spot and it didn't matter if it was only a subset of the members who weren't playing nice because the whole guild would be massacred. Even in video games it matters who you hang around with. It starts out with little decisions like what server you belong to or what college you chose to attend, but you can't ever complete your achievements if you don't get nice guildees to help. You always choose. You can always change guilds and switch friends. You don't have to hang out with the immature idiots who won't get on their mesmer characters and portal you to the top. You can find people who will enjoy your company and continue to fight for you even after you fail to complete the easy puzzle on your own.