success and failure in commercial space flight

Consider the recent successes (and failures) in commercial space flight. For example, read up on some of the recent work by Space X (https://www.spacex.com/) and/or Blue Origin (https://www.blueorigin.com/). What engineering risks did the designers have to consider when designing these rockets and its launch systems? Can you describe at least four? (I am sure there are many). Can you find any comments from the engineers (or the heads of these companies, for example Elon Musk) about what they learned from past failures? Please include any references used. (at least 300 words)