europeforvisitors - 5:49 am on Aug 19, 2005 (gmt 0)

camera enthusiasts also buy lots of digital storage cards, but adsense won't put up an ad for that on a tripod page.

Probably not, but so what? AdSense is a network that aggregates impressions and clicks from many different sites. As long as AdSense can serve enough ads for digital storage cards on contextually targeted pages, the ad budget gets spent and the advertiser gets his or her leads.