Just continuing the thought experiment... Would this be sufficient? It could result in 3650 subdomains created every year.
I also wonder whether it could be gotten around by creating throwaway panel users will full privileges. Your main account could create 10 throwaway panel users per day. If each can create 10 subdomains, that's 100 subdomains a day. In fact, since the "throwaway" panel users can create other panel users, there's actually an infinite number of subdomains that could be created by the virally replicating panel users.
Maybe the API calls could be limited by the underlying account rather than by user?
I wonder if interactive panel accounts could be made to not be subject to this? Or in the ideal case, they could be made to not display the captcha until 10 qualifying "API" events were made!
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