Front to back

Does anyone know of any research about this:

Theory: people sometimes (often?) choose web activities by medium, rather than by content type.

So as well as saying "I want news" people sometimes say "I want photos" or "I want video" or " I want blogs". So aggregating lots of examples of the same medium can be more effective that addressing one genre of content with several media mixed together.

Consider:

• Mail and Guardian "news in photos" site
• Flickr, Youtube etc

Vs. a site like BBC news which mixes video in with copy. (Except they've also got a video and audio section, I note).

Is this obvious? Does anyone have any additional evidence?