Yeah they've hit their max new user count. But keep checking your e-mail box... they've stated that they will allow more users periodically. Since this involves a lot of server-side processing, you can see why they need to keep a handle on the number of people using the service in these early stages. I'm sure it won't be long before we're all deepfishing.
It's a neat app for sure. Thunderhawk's WM business is about to plummet