No Default Defence.
Unexpected iPhone bills, Facebook privacy controversies and ongoing wifi security issues. All caused by ill-conceived default positions. Default positions that have technical manifestations but which, at heart, are attitudinal problems.
Since you can never truly know what each individual customer wants in terms of the myriad options you offer; since you cannot be sure how they will perceive any action that conflicts with that; and because your primary objective must be to avoid annoying any customer, your default mindset should be obvious to you.
It must be the one that minimises nasty surprises and inconvenience and not the one that maximises what you perceive to be opportunities, be they for your customers or for your cashflow.