There is some amount of manual labor needed to get someone signed up. I won’t say exact numbers, partly because I don’t know them, but to give you a sense of the situation:
Say that n users can be added to the beta in the amount of time available to do that. Then every now and then the application is updated, and another n people are added, eventually everyone is signed up.
Unfortunately, or arguably fortunately, on the first day 10n people signed up. You may well have been within the first 10n people, but not yet been reached in the list.
Aaron hinted at giving out some related information in the live stream next Friday (March 11th):