I did a little accidental arbitage back in 2005. I advertised using adwords using carefully chosen key phrases, and paid a few cents a click. A click on one of my sites would net 10 times that. I made a very small amount of money out of it even though my intention had been to promote a new site. Presumably my advertisers were using a more broad match.

It's impossible to tell which keywords people bid on to appear on your site. Advertisers might be paying much more than they need to.

Also advertisers might still be gaming the system. If you can't see how an advertiser is making money on their clicks then chances are they aren't paying much for them. That's what your competitive ad filter is for.

accidental arbitage

I like that!

I am about 50% organic 50% adwords they track totally separately in landing pages and duplicate website pages. At present the adwords side is even money $1 for $2 back or $1 net, the last 3 months it has been half that it just improved this week. 2 years ago it was 3x that.

I have a totally legitimate 12 year old software download site I just use adwords as an extra bump, I could exist without it.