Not just a talk but rather a performance by Neal Ford, it warned us against the levels of abstraction we are so used to add over complicated things, so that we forget what lies underneath. It reminded me of Joel Spolsky's Leaky Abstraction.
Neal Ford gave some rules about abstraction layers. The one that I felt was the most important was that a layer of abstraction might cover 90% of the features of the layer below it, but since users would still want in some cases to access to the remaining 10%, the upper layer should provide for a way to do it.