Last weekend, we had to disable new invitation requests to address an influx of accounts flooding the Archive with spam works. While our Abuse team has been banning these accounts and deleting thousands of spam works, the problem persists and would most likely get worse if we sent out invitations again.
We have decided to keep the invitation queue closed for the time being while we take steps to prevent spam from being posted in the first place. This means you will not be able to create an account unless you have previously received an invitation from either a friend or our automated queue. (If you requested an invitation before October 22 and have not received it, please check your spam folder and, if you use Gmail, your "Social" tab. If you are still unable to find your invitation, you can contact Support with your specific request.)
We very much regret denying invitations to legitimate users, but as the amount of spam being posted is affecting everyone's user experience, we currently see no other way to address the problem.
We will reopen invitation requests as soon as we can, although we do not have an estimated date at this time. When requests have been reenabled, the "Get Invited!" link will return to the homepage, and the Invitation Requests page will include a form to add yourself to waiting list. (The option to request invite codes for friends has been disabled since the last spam wave, and we have no plans to bring it back in the foreseeable future.)