This is an interesting article from the Nation on the escalating violence in Monterrey. It describes how with the twilight of the PRI, Mexico's long-standing single political party, drug cartels no longer operate in an orderly fashion, respecting civil authorities and one another's territory. With no more monopolistic institutional power (neither on the part of government nor of the cartels), it's open season, open warfare as greedy groups grasp for more and more territory and power. Essentially political democratization has led to hellish violence and disorder.
This reminds me of what happened in Colombia when authorities took down the major drug cartels in the early 90s. There arose more violence and chaos, as everyone from smalltime hustlers to armed leftist insurgencies now got involved in the drug game. Colombia's recent spell of relative peace and stability is welcomed by us that live here, but it's bittersweet to know that we're only in peace because the violence has been exported elsewhere. And above all, we know that things could easily change, with trafficking and violence shifting once again away from Mexico and returning to our fair country.