lappert2001 - 10:26 pm on Feb 14, 2012 (gmt 0)

Granted, there's no way to know every single ad that has popped up in Google Adsense, but they would know about those Adwords customers that have directed their ads to your web site. The advertiser that contacted me directs their ads to my site, and I see them almost every time I load particular pages. Moreover, they take up entire ad insertions, that might otherwise be populated with 3-4 smaller Adsense ads.

Indeed I do have some smaller advertisers that bought space with up first, and then appeared later in Adsense, but here we're talking about a more significant player.