The whole point was to make a Mac client, not to "spam the system."
I'm sure it's more complicated than that however, like client side rate limiting or something.
I bet they would put the rate limit in the client, since they did that with the banned word list, but rate limiting would make more sense at the server. Maybe they did both.
Now you could fire up a new VM for each client or use a botnet to do your bidding. Oh, how the Internet has advanced.