(Reuters) - Shares of Amazon.com Inc were down 3% on Friday, as investors were let down by a lower-than-expected sales outlook and surprised by slower revenue growth at its lucrative AWS cloud business.As many as 16 brokerages cut their price targets on the stock, with many saying higher costs to keep its one-day delivery Prime members happy played a big part in weaker profits."Going forward, it is difficult to assess when Amazon will once again begin to deliver profit upside. We think that the..