How child porn killed my app called YayNay

Yea. As a server admin with 18 years under his belt, here's the first thing you need to know about the internet. If you have an anonymous service a basic tenant is moderation and spam fighting. I've seen a hundred good ideas that would never work because they don't take in to consideration that 'People are assholes'.

Any system that does not fight spam will quickly become only spam (porn considered as spam in this case as it's not the point of the app). Any image rating/manipulation program will quickly become only spam and porn unless heavily moderated.

TL;DR: If you aren't considering spam and security issues when developing apps please stop. Either read up, in detail, on how to do it correctly or add a developer that understands the issue.

1 — number of child porn accounts we kicked and reported

Just 1? Wow, you gave up way too easily.