[HuangA]

Yes, there are certainly benefits to it. In your described case though, I'd still take additional percautions. I have had people coming to my site and first thing thy said was something like:

I just found this site from google, comparing to <competitor site>, this is way better and easier to use. Thank you for making this possible!!

If you do add competitor site to your keyword list, I'd recommend giving it some flexibility (ie: allow two occurances in post before it trigger moderation, and three or so before it trigger reject).

As mentioned, I'll look into coding an auto ban level during the weekend coming up, and update this again

PS: I'm considering a further "profile" system where we can create different sets of keywords/weights, so we can target spam better; but one problem I can see is if we add too many sets of profiles, the math required will probably take more CPU time... Any opinions on this, anyone?