IMHO if a user sees a thread like "Hot sexy russian woman looking for man" they should report it.
I have just woken up to eight reports from that thread. Many thanks to the users who took the time to report it. On checking I see the thread has already been removed, and the user has been dealt with. I would rather eight reported than none. Reports are received as a PM.
I agree that replying to a thread is not a good idea, it just gives the thread more airtime than it should have.
In answer to your question skelly831, only one report is required. Generally one is enough for it to get noticed pretty quickly. I get an email to my Google account (which I can view at home and work) when I receive a PM.
In the example of the thread above it seems that it was posted at a time when the mods were inactive, which meant that it was alive for around six hours. In other circumstances I have managed to remove threads before anyone else has seen them.
Thanks for creating this thread kjoonlee. After looking at the thread quoted it seemed like some questions needed answering.
Edit: Damn! With my just-woken-up typing speed I was beaten to the punch.