conroy - 9:32 pm on Jul 29, 2004 (gmt 0)

Hence the name "contextual advertising".

"Spam" is content as well.

Also, who says it is declining? It is booming. And I agree with gopi that there is better ROI on the spam pages than high quality sites oftentimes. You can test this yourself by running an affiliate program instead of adsense on the spam pages.