I don't see an issue if 20 new clans are created in a week, it should be open to everyone. If they're not of great quality then they won't get past being unofficial, no big deal.
I can get behind maybe trying to stop the same person spamming clans. Instating a cool down period or something that will stop someone making a clan for say, 2 weeks after just making one.
We'll check to see if something like that is possible.