The number of H-1 visas is capped at 65,000 per year.
http://www.workpermit.com/news/2005_08_15/us/h1b_visa_quota.htmThere are nearly 18 million professional and business services workers in the United states, 137 million non-farm workers. You can see that, percentage-wise, the numbers are miniscule.
http://www.bls.gov/news.release/empsit.nr0.htmThe real threat is not from foreign workers coming to the US to work, pay taxes, spend money in our economy and eventually become permanent residents (if they're lucky).
The real threat is from outsourcing of jobs outside the United States, where the workers are paid a fraction of US salaries, pay no US taxes, spend no money on our economy, and eventually become an establish competitive threat.
http://www.physorg.com/news132580556.htmlIt is easy, when economic times are tough, to look for a scapegoat to blame, and foreign workers in the US are an easy target.