Amazon had a solid second quarter and the really important trend for the business hasn't changed one bit.If you are old enough you will remember a time when Amazon.com (AMZN 1.44%) was a fledgling online book store. But that was a long time ago at this point, with the company's online presence now so ubiquitous that, for many consumers, it is the first place they look when shopping for anything.The interesting thing here, however, is that Amazon has now grown to the point where its retail operations aren't ...