Which is why I love it. Sadly, years and years of MMO's have drilled into player's minds that others are your rivals. There's plenty of times when I'm questing and reviving NPC's, and people will walk by and revive another one. I always end up getting up, going to where they are, and help them revive that one. Then we go back and revive the one I already worked on.
Same with fighting. I'll be fighting something, a guy doing the same quest will attack a separate monster. I'll then lead mine into his, and make it a group thing so we both get the xp/loot/quest reward.
In other MMO's, all players are rivals. Even those in the same faction. In Guild Wars 2, everyone is an ally. And I love it.
Also what's great about the game, you can level up wherever you want. From the start you can go to any starting area, and level there. And since the game de-levels you when you go into a lower-level zone, there's no high-level players griefing people by killing everything. The mechanics of the game make griefing a very hard thing to do, if not outright impossible. Oh, and when de-leveled, if you fight in a low-level zone, you still get the same amount of experience you would if leveling in a zone equal to your level. This means you're always leveling where you want to level, and not where the game tells you to level. It's also great if a friend just starts. Since you'll be de-leveled, you and him can quest together wherever he wants and it won't be a "sit back while the high level guy kills everything" deal.
And the skills... the game does away with normal skill trees and the whole "tank/healer/DPS" trinity. Everyone has a healing skill. Sure some are better at it than others, but everyone can be that supporting character if they want. And there aren't any skill-trees. Each weapon has its own skill-set and gameplay style. This means you can fight with the weapon you want.
So in Guild Wars 2, you're playing how you want, where you want, in a group where everyone benefits. It's just... why the hell did it take so long for something like this to happen?!