Grits for Breakfast has a great post on a sobriety checkpoint bill being considered by the Texas Senate.
Sobriety checkpoints can help secure the greater good, if they are designed -- procedurally -- to narrowly focus on drunk driving. If not, they allow for random, arbitrary fishing expeditions, a hallmark of totalitarianism (at its most extreme anyway).
He outlines a bill designed to do just that, which he still opposes on principle, but his discussion helps clarify how procedural restrictions are essential in order to both protect the general welfare while securing individual liberty. In essence, this is a Fourth Amendment issue. What makes a search reasonable?