http://www.p4rgaming.com/?p=481

The following excerpt discusses the difficulties behind malicious drawers in the Miiverse:
Iwata: I agree. The unique feature of the Miiverse is being able to send drawings, not just text. But since the advent of the internet, there have always been those who have used it for unsavory purposes.
Kurisu: Right, auto-detection of bad words is very simple.
Iwata: Yes, text messages may be easy to moderate; however, drawings are much more difficult.
Yuzawa: (laughs) I think I know where this is going.
Kurisu: Let us get this out of the way then. (laughs) We anticipated that some users would draw…
Kato: Can we even say the word?
Iwata: Go ahead. (laughs)
Kurisu: Ahem, uh. Some users would take to drawing *****es.
Everyone: (laughs)
Kurisu: Well, it’s true. It seems to be more of a phenomenon found in the west.
Motoyama: Yes, we never had such a problem with our Hatena services. But, when we brought Hatena Flipnote to the West, we were caught off-guard by the amount of *****es drawn by people.
Kurisu: So the team and I had to come up with a way to create a system that auto-detects those types of pictures.
Kato: Kurisu-san suggested we study different types of *****es in order to create figure out the relative shape and size people would draw. We spent a week doing that before we realized that we should have been looking at drawings of *****es rather than real-life pictures. (laughs) We were very embarrassed about that.
Kurisu: My judgement on these types of situations is poor. (laughs)
Motoyama: After a week, we made very good progress on the system. Then we tested the system with Nintendo of America and told them to start drawing. It went horribly.
Kurisu: What we learned is that people enjoy drawing *****es. Multiple ones. (laughs) The system was not prepared to handle that.
Iwata: I do not think your team anticipated how difficult this would get!
Kurisu: No. (laughs)
Yuzawa: I was disheartened myself. We spent a few more weeks trying to get a system working.
Motoyama: Nintendo of America really took the system to its limits.
Yuzawa: You know what surprised me. No one drew a single ******.
Everyone: (laughs)
Iwata: So, in the end, it all worked out?
Kurisu: Yes, we can safely say that we have a very good system to detect ***** drawings. Hopefully player’s Miiverse experiences will be a fun one!