I have an old site which is horrible, never got round to fix. It is picture based and almost no text at all. So I thought of starting a very dear friend in adsense. I was sure that this site will not be accepted and that would motivate him to start improving. but he got the
WELCOME TO ADSENSE
I would not even link to this site if they paid me. If this is the adsense policy then in the long term serious publishers will suffer.
As an AdWords advertiser, I often check the referer links to see which sites display my ads. I must admit that there are quite a lot of garbage websites around, but on most sites, the theme of my ads matches the theme of the pages where those ads are displayed. Therefore I keep the content network switched on, because a visitor is a visitor, regardless of the previous site he has visited.
As a regular surfer I would like to see the quality of those sites improved, but as an AdWords advertiser I don't mind too much. If the traffic from those garbage sites is targetted, it is worth the money.