What is an example of a competitive industry and why is it competitive?

The smartphone production industry is one of the most highly competitive industries in the US at this time. The main competitors include Apple (iphone), Research in Motion (Blackberry), and Palm (Treo), along with other competitors as well. The definitive explanation of the level of competition in an industry has been presented by Michael Porter. The amount of competition in an industry can be determined and described according to the the following: 1)barriers to entry into the industry, 2) available substitutes for the products produced by the industry rivals, 3) the power of the industry rivals over their customers, and 4) the power of the industry rivals' suppliers over the industry rivals.