With the magic of computers you could deliver 400k versions of your ad. Each tailored to the site where the ads are being displayed (or even more - tailored als

With the magic of computers you could deliver 400k versions of your ad. Each tailored to the site where the ads are being displayed (or even more - tailored also to the specific user). Probably most of these sites have very distinct audience, so you could build quite targeted ads. If you are just spamming the same ad everywhere, then I can certainly understand why it does not make difference if it appears on 5000 vs 400.000 sites if the ad display count stays the same.