Tim O'Reilly suggests that at least part of the reason for Amazon and Google's success comes from their open API. This allows people to access their information in ways that fit people's individual needs ("rip, mix, burn"), giving them a massive advantage over monolithic proprietary apps. He gives the example of their own use in O'Reilly - they monitor the 'technology' section of Amazon's books for how well their books are doing, their prices vs. their competitor's prices, what new books have been released and so on. With Google, we're seeing this as it happens as people continue to extend maps.google.com to tie in with other services, such as Flickr, producing Geotagging.
Well, the BBC must have been listening. Yesterday, they launched BBC Backstage, which is set to provide a one-stop-shop for all of the BBC's web content, from their RSS feeds to their Search API (not available yet). Most interestingly for the casual user (read: non-developer), they're also using this as a way to track the ways in which people are using the BBC website, such as providing a way for people to provide their own "external links" for stories, or giving stories del.icio.us-style tags.
I look forward to seeing what sorts of things people come up with.