Meta-Moments: Thoughtfulness by Design is a great post by Andrew Grimes on the benefits of making users pause and think in certain areas of an interface:

Meta-moments can provide us with space to interpret, understand, and add meaning to our experiences. A little friction in our flow is all we need. A roadblock must be overcome. A speed bump must be negotiated. A diversion must be navigated. Each of these cases involves our attention in a thoughtful way. Our level of engagement deepens. We have an experience we can remember.