I think one secret is community-based ads. I'm happy to receive ads about products directly related to sites I frequent. For example, things produced by YC... I

I think one secret is community-based ads. I'm happy to receive ads about products directly related to sites I frequent. For example, things produced by YC... I would be happy to peruse an "ads" tab (next to "jobs"/"submit") by my own volition. 2600 magazine does the same thing... ads by subscribers only... and they're always interesting. That's the key. Find ads that people WANT to see, so much that they're almost willing to go out of their way to see. Then again, if you really have high enough volume, why can't you just try EVERYTHING and then only show ads that get high CTR? Isn't 5k impressions a sufficient sample size? What about using graphs of campaign clickthru rates for individual people (a la directededge)?