Shifiting the focus of Immigration Enforcement Policy?

In what appears to be a change in the methodology of immigration enforcement, the Immigration and Customs Enforcement initiative (commonly referred to as ICE) has announced an "audit" of 1,000 different companies, looking at whether or not these enterprises knowingly hire illegal immigrants. At first glance, this seems to be a change in tactics. As pointed out in the article, normal fare for ICE consisted of mounting raids at work places, looking for undocumented workers. These raids seem to have placed priority on immigrants rather than offending businesses. These new tactics seem to be a reversal of this. However, the article points out that the list of businesses being targeted are not being publicly named. Furthermore, while 1,000 different businesses are certainly not a trivial number, I wonder if these audits are only scratching the surface. What types of business are the audits targeting? Do they represent the traditional, large scale employers of illegal immigrants such as the agriculture industry, or service industries (as the article suggests)? Do the 1,000 business as a whole target a certain business, and target a significant quantity of such businesses, or is the selection random, or not target a meaningful number of enterprises? The thrust of my questioning leads to one overarching concern; is this a meaningful gesture or not? If this "audit" does not target the traditional employers of illegal immigrants, or does not target a significant market share (that is, if the audit doesn't do enough "damage" to employers of illegal immigrants in general), then it seems to me that this action is a meaningless gesture. Whether or not this is the case, the audits are having an impact in the behavior in companies. For example, the article states that a clothing manufacture dismissed over 1/4 of its work force (~1,800 employees) after an audit raised concern over its hiring practices regarding illegals. The business community as a whole, the article goes on to state, is reacting as a whole. However, how comprehensive and what the longevity of this reaction has yet to be seen, as this is only the second audit of its kind to be conducted.