Shares of Amazon.com (AMZN) tumbled more than 10 percent in extended hours trading on Thursday evening after the online retailer issued quarterly results which fell short of Wall Street forecasts. For the fourth quarter, profits were $1.00 a share, estimates had been for profits of $1.56 a share. Net sales were $35.7 billion, pretty much in line with forecasts. So, why the big miss? Well, it looks like operating expenses surged more than 20 percent to $34.6 billion. The retail giant has been doing a lot to roll out new services for its Prime loyalty program which include original video programming and one-hour delivery in certain cities. Another reason for the earnings miss, it also appears that growth at Amazon's cloud services business, known as AWS, is slowing. In the third quarter, sales at AWS grew by more than 78 percent. in the fourth quarter they grew a little less than 70 percent. TheStreet's Ruben Ramirez has details from Wall Street.