What is the most practical way to make sure Users don't upload photos onto my site that they shouldn't (e.g. nude photos)?

I was going to write a PHP script that marks the "photo_approved" field as "no" in my "member" table, and then manually review all new photos.

Someone I was talking to suggested just adding a "report" button and let other visitors to my site monitor things for me.

Thoughts?


Debbie