As Business Week pointed out in an article last month, the employers using the overwhelming number of H-1Bs are offshore outsourcing firms. These firms' whole reason for being is to ship work overseas, not to use the H-1B program as a bridge to immigration. They shuttle foreign workers into the U.S. to get trained so that they can then take that work back home.
We've come a long from worrying about brain drain from developing countries. This alarm indicates, to me at least, that intellectual capital is beginning to seek frontier market opportunities. International brain circulation is a very real phenomenon, but that's no reason to discourage mobility.