Contextual advertising is a form of advertising where ads are displayed on a website based on its content. These ads are served by automated systems which try to display them on relevant pages.
Google AdSense is one example, where ads are related to the words found within the content of a page. This type of advertisement is praised by publishers because having relevant ads placed next to a piece of content, the click-through rate is high. But this also attracted controversy, just like how people thought that the placement of ads related to messages in Gmail is a breach of privacy. The issue has been settled already but it’s not the only one related to contextual ads. When publishing news content, ads served by automated systems instead of humans can become subject of controversy. The recent death of Dennis Hopper on the news was an example.
An ad about life insurance placed beside an image of Dennis Hopper. Relevant ads, eh?
I later found out that CNN had earlier issues with contextual advertising. I guess news websites need to be more aware about advertising and implement measures (filter keywords, exempt ads from showing, etc). Otherwise, news like this will generate ads that might raise eyebrows. To advertisers, it could mean a wasted media buy.