Get a cup of coffee and read this report.
The AFL-CIO has weighed in on the U.S. visa situation (i.e., the situation involving L-1, H-1B and other work permits). They have produced a report titled, Gaming the System, and it is an interesting 52-page read.
This report looks at the effect of U.S. visa policies, especially around H-1B visas. The authors focus much of their research on the STEM occupations (i.e., Science, Technology, Engineering and Math) and on the education sector. The authors did a fairly good job of chasing the policy, law, lobbying and results of same since the mid-1990s.
Some of the points this paper makes are pretty hard to dispute. For example: