Hydraulic stimulation in low permeability formations is successful when it generates a large stimulated fracture surface area. Sweet spots are regions within a play or along a well where production is especially prolific. Sweet spots may be related to matrix quality such as permeability. Sweet spots may also be related to formation properties that encourage fracture network quality – the ability to create high stimulated fracture surface area. In the literature, there does not appear to be agreement on the processes that generate a quality stimulated fracture network. I will review different theories and discuss pros and cons of each. I will also report on results from a sensitivity analysis study that used CFRAC (Complex Fracturing ReseArch Code), a discrete fracture network simulator that couples fluid flow with fracture propagation, conductivity evolution, and the stresses induced by fracture deformation. The results suggest that the tendency for shear stimulation – the tendency of natural fractures to slip and experience irreversible conductivity enhancement in the formation – is one of the most important variables in determining fracture network quality. I will discuss efforts towards addressing how this variable may be predicted and quantified, and how this concept might be applied to formation evaluation and sweet spot identification.