One of the things that keep people worried about Mexico is the state of drug use and the drug trade here. The situation has gone so bad that some quarters claim that certain Mexican states are already on the verge of descending into "drug state" status, just like how Colombia was much of a narcotic nation last decade.
According to this article from UPI.com, certain academics claim that there are certain locations in the country where the drug cartel is rampant and where people can be hardly governed. They also claim that this lawlessness will soon expand to neighboring areas if preventive measures aren't done.
Edgardo Buscaglia, an expert on organized crime from the Autonomous Technological University of Mexico, these states will be soon be like Colombia 15 years ago, which is characterized by the increasing power and authority of the drug cartels and the left-wing insurgency groups. Violence was then rampant, while bribing government officials allowed the wrongdoers to continue.
An example of this gradual slide towards drug cartel rule are the cancellation of the elections in Tamaulipas state because of the fears that the drug cartel has already infiltrated local politics, and the redeployment of army troops to Chihuahua because of the fear that the cartel is already starting to control the smaller towns located along the borders of the nation.
It also isn't helping that these drug cartels are fighting each other over the control of these towns. Massive violence is present in these locations as the cartels try to eliminate one another. The state of violence here may already be regarded like some sort of low-key civil war--and that is never good for the Mexico and even the United States, which could get involved in the drug wars very soon.
Fortunately, much of the areas where tourists are centered are still relatively OK, so you can still pursue your Mexican vacation. But then again, we don't know until when the peace in these areas will last so better enjoy your vacation while it lasts.