The Importance of Good Flashing

What happens when flashing is poorly installed around windows?
The feature photograph shows what might show on the interior, but the following photographs show what may be hidden in the wall.

Figure 1 Water staining, mold growth and decay around window.

Figure 2 Water staining, mold growth and severe decay under window.

Figure 3 Water staining, mold growth and severe decay under windows.

Figure 4 Water staining, mold growth and severe decay under window.