Builds on my recent observations that it is the questions you ask as much as the answers you get that are important. And you can't ask the right questions unless you have complete data as you don't understand the big picture.
In my early days as a product manager I relied on samples to research consumer behaviour and motivation. Big Data offers the change to analyse the big picture and not rely on sampling.
Advise you to link through to John Balls's blog for the tale of the " Blind Men and an Elephant" to realise the important of seeing the big picture including data outliers.
Outliers may indicate a serious flaw in your picture of the world and/pr the algorithms driving your business
Big data also should prompt us to question assumptions, especially in marketing. The reason is that our customers' behavior and expectations have changed so radically, we need to ask if our marketing has changed in kind? How has your marketing changed in the last 5-10 years? Have you changed how you’re organized and how you do your planning? Has your approach to engaging your audiences changed? If the answer is no to any of those questions - simply ask yourself why and then think about whether or not the answer you get is good enough.