Shares of e-commerce and cloud computing giant Amazon.com (NASDAQ: AMZN) have delivered incredible returns to investors. The stock is up 68% over the past year, nearly 300% over the past three years, about 1,900% over the past decade, and more than 86,000% since the company went public in 1997. It's been quite a ride.But with Amazon now valued at more than $800 billion, it will be difficult for the stock to put on an encore performance.