Whatsapp is having the same bot issue, with large groups getting spam from bots. The problem is even worse than in twitter. So now the group admin isforced to

Whatsapp is having the same bot issue, with large groups getting spam from bots. The problem is even worse than in twitter. So now the group admin isforced to close groups by requiring group admin approval. This is clearly the best type of moderation: localized and user-driven. It is not top down.