Update: ArenaNet has, at some point, quietly resumed sales of Guild Wars 2 on their site. No major announcements were made, and we suspect this may have been intentional and part of an effort to avoid another massive influx of players. While some bugs persist, major issues previously mentioned -- such as the Trading Post -- appear to be resolved.
August 30: ArenaNet has just announced that, with a heavy heart, they are temporarily stopping first party sales of Guild Wars 2. If you've been keeping up with the MMO's launch, then you're probably somewhat aware of the rough situation in-game right now.
What it comes down to for developer Anet is providing the best possible experience for the Guild Wars 2 player base, and as of now, they feel that's beyond their reach. As a result, game sales via the official site are at a temporary halt, until the devs have managed to fix things up. If you want the game, however, you can still grab it from third party retailers.
Here is the official statement from Anet, posted minutes ago on the official Guild Wars 2 Facebook:
Ensuring the best possible play experience for our fans is our highest priority. We’ve said before that we would be willing to temporarily disable first-party digital sales if we felt our high player concurrency may compromise player experiences. We have now reached that point.
Effective immediately we have disabled sales via buy.guildwars2.com. To be clear, box and digital sales are still available via our retail partners. We are tracking our concurrency closely while expanding our infrastructure. We’ll re-enable first-party digital sales as soon as we feel that we can do so safely. ~RB2
Over the last few days, numerous problems have popped up in-game, from an unstable Trading Post that can't seem to stay online to the disabled mail system (should be online now). Yesterday, ArenaNet posted an explanation on Reddit addressing some of the bigger issues.
So it's pretty busy up in Seattle for the Anet folks, not to mention kinda rough on the Guild Wars 2 players, but at least they're keeping the community in the loop.