Instead, if you're a developer, fill out the form at
https://services.google.com/fb/forms/wavesignupfordev/.
Or, if you're not a developer, fill out the form at
https://services.google.com/fb/forms/wavesignup/.
These are the only ways to get an account.
* For developers --
http://googlewavedev.blogspot.com/2009/07/google-wave-sandbox-update.html
* For non-developers --
http://googlewavedev.blogspot.com/2009/07/google-wave-updates-from-todays.html