It seems any one can flag your pictures, stash, mumms NSFW. I have noticed some people do it out of spite, if you don't agree with them, or if you won't talk to them.
Which in my opinion is really messed up. I believe if Cherry Tap is going to allow anyone to decide on what's NSFW then the person they flag they shoulld be allowed to know who it is.
Over 70% of the NSFW flags are rediculous. For this to be an adult site there is a lot of juvenile behavior allowed.