I plead with all of you to read the following blog posts. They provide very compelling evidence that there is NO shortage of U.S. citizen/permanent resident STEM workers. The H-1B debate usually devolves into a match between two opponents who only have anecdotes to support their positions. The following blog posts offer DATA (with sources).
http://immigration-weaver.blogspot.com/2011/10/show-us-workers-here-you-go.html
http://immigration-weaver.blogspot.com/2012/05/stem-dont-let-this-happen-to-your-job.html