Amazon started out as a few guys in a garage selling books that were mostly technical in nature (programming languages, computer hardware, engineering, etc.). If you COULD actually find these on bookstore shelves, they cost full MSRP and were several editions old.
Amazon sold below MSRP, offered cheap shipping, and had the most current editions available.
When their purchasing and distribution systems grew with the Internet, they branched out from only offering books.
I see Amazon as a pure success story. A service filled a niche market and grew to dominate the entire US online shopping industry.
Nothing is stopping anyone else from developing an even better business model in the future. It just takes an innovative mind and enough public demand to help it compete.