Sadly, in Oaxaca this past year, there have been many problems and disruption.
As it mentions in this article, the teacher strike that has happened every year for the past 26 years that usually lasts only about 2 weeks and is generally peaceful, has grown into a full-out protest. The first American was killed this past week and it is finally waking the government up to the fact that something needs to be done immediately for this beautiful city before it is completely ruined.
Here is the article from the Washington Post describing the police invasion of Oaxaca's city center...http://www.washingtonpost.com/wp-dyn/content/article/2006/10/29/AR2006102900180_pf.html