Very good idea ...The users will be glad to have this feature.

I was thinking about a flagging system too, kinda like craigslist.

Here's how it would work.
A member sees a inappropriate post and clicks on the FLAG button, a dropdown menu with several fields for the flag, such as spam, cursing, something illegal, etc. The member clicks on the appropriate field and clicks OK.
After say...5 flags the post is removed and sent to a section that only the administrator can view. And it show the names of the members who flagged it, incase a member goes on a flagging spree.