Information design in Web 2.0 is simple, it is social, and it embraces alternate forms of navigation….. The design of today’s Web applications is being led by a principle of simplicity….. There has emerged on the Web a trend towards socializing things which are not inherently social such as books, photos, videos, and text such as news articles, papers, and posts….. In addition to websites which socialize media and applications, there are websites which are social for social’s sake. These websites are all about connecting people and building community. They are the social networking websites such as the MySpace, Gather, Facebook, and Ning networks.
The video below from ZDnet, which covers Mashups, provides another part of the story – an explanation of the extensive influence of APIs in creating the flexibility of Web 2.0.
What is a Mash-up