What America's most interesting companies have in common.

Ask yourself this question: Aside from the companies where you or members of your family work, how many do you actually care about? We think that for a lot of us, there are only four: Starbucks (SBUX), Apple (AAPL), Google (GOOG), and Amazon (AMZN)—call them the SAGA companies. Of course, reducing what's exciting about American business to SAGA is an exaggeration—but stay with us for a bit while we make a case that these four corporations represent a distinctive, and distinctively American, contribution to 21^st -century capitalism.

The SAGA companies do very different things and are of hugely different sizes: Google's market capitalization is about $158 billion; Starbucks is down to below $12 billion. Yet they share some remarkable traits. At the most basic level, each has transformed not just a specific commercial marketplace but some important aspect of contemporary life—computing and music for Apple, information and advertising for Google, coffee for Starbucks, books for Amazon. In doing so, each has had an appreciable impact on our daily routines, taken on a looming presence in popular culture, and often engendered an intensity of feeling more frequently associated with tastes in entertainment or political views. Together, they've created a new model of business innovation, culture, and values.

But what, really, do the SAGA companies have in common? Here's a start:

They have a ubiquitous, everyday presence. Ubiquity doesn't necessarily make SAGA companies global market leaders; the worldwide proportion of computer users who own Apples is small and will probably never catch up to the formidable PC. But in many countries iPod usage is surging, and all the world wants an iPhone. As for the others, Yahoo retains a slight Web-traffic edge over Google worldwide, but that will not likely last much longer, and it is Google whose name is synonymous with finding information on the Web. (We figure that between us we perform 100 Google searches a day and can easily go for weeks without using another search engine.) Amazon may not dominate e-commerce sales outside the United States as much as it does inside, but in few of the countries where Amazon operates Web sites is there a competitor that sells more books online. Starbucks manages to be everywhere and also across the street.

They reflect the comparative advantage of today's America ... Dial back to the Fortune 500 list of 1958 and there's no mistaking the difference: A half-century ago, the iconic American companies were about making and moving stuff: General Motors, Ford, and Chrysler were all in the top 15. Oil companies and steel manufacturers filled all the other top slots, along with General Electric, Eastman Kodak, and the company still widely called in those days International Business Machines. Granted, SAGA companies do not rank that high on today's list, although they are often more profitable than firms that bring in larger revenues. Nonetheless, they represent the dramatic shift away from domestic manufacturing and toward an idea-driven, consumer-focused, value-added economy. It is also not coincidental that all four companies are based on the West Coast, reflecting the shift in America's demographics and centers of innovation.