Amazon.com (NASDAQ:AMZN) is the stock that continues to amaze. On Wednesday, it traded up another 1% in early trading, marking its eighth straight day of gains. In just that eight trading day span, the company has seen its market cap increase by over $30 billion which is more than the entire market cap of Target (NYSE:TGT). The S&P 500 Retail Industry Group currently consists of 32 companies across a wide variety of the retail landscape, but interestingly enough, Wal-Mart (NYSE:WMT) isn’t one of them as it is considered part of the Food & Staples Retail Industry Group. Not including the Food and Staples retailers (where AMZN is also growing an increasingly large foothold), AMZN continues to steadily increase its size within the Retail group.

With a market cap of over $400 billion, AMZN is by far the largest component in the S&P 500 Retailing industry Group, accounting for more than a third of the group’s market…