I've just been pointed to this valuable paper from the Centre for International Communications Research at Leeds University. "News Agency Dominance in International News on the Internet" by Chris Paterson demonstrates how there may be a multitude of online news sites but they nearly all rely on two sources - Reuters and AP. The BBC gets a rare and honourable mention for having its own newsgathering and a wider range of sources.
It suggests the internet is "a mass medium providing mostly illusory interactivity and mostly illusory diversity...."
"The evolution of the online news agency has laid bare the news industries' near total dependence on a few wholesale news providers and the limitations on public discourse that it inevitably yields."
"In the longer term the industry must invest in more original reporting as an alternative to the few genuinely international news organisations now on offer, and give more prominence to buying, and properly translating, original non-English reporting from around the world. Without such change, new media will continue to present to most users the dangerous illusion of multiple perspectives which actually emanate from very few sources."