Russia, India, Brazil, China, too much cheap labor
I worked at an engineering company here in the US that staffed it's workforce with about 80% offsite foreign labor and few dozen onsite Visa workers (hundreds of people for this particular project/product). There were a few of us US citizens left to oversee the work (I'm sure that was a contractual requirement with the various customers).
To facilitate the sheer number of different places that the work was distributed, each foreign site would send a few people over to the US to help with the interactions (language barriers, etc..). Of course, the company didn't get appropriate work Visa's for these people, so they were technically here on a travel Visa, and therefore couldn't do anything actually considered work. No idea what was in it for the people who made the trip? A free trans-continental flight and hotel room? Not sure this was entirely above-board, but I can only imagine the bonus some higher-ups must have gotten for doing the work with foreign nationals working at a fraction of the cost and who would apparently do anything, including travel to the US without getting paid.
At that particular job, I was actually working as a contractor for a US-based Indian contracting firm. Not sure how all that actually worked out (the whole ordeal was just stressing), but I get the feeling I was one of the few US citizens they employed in the US. I do know the few contractors actually there on a work Visa (i.e. legally) made far less than I did.
This is one of the few things I agree about with the current president, too many work Visas. I'm fairly sure the quality of higher education in the U.S. is better than in India. That whole excuse about not having enough domestic talent never sat well with me. If nothing else, the cost of the Visa's should be applied to scholarship funds to educate more Americans to replace the apparent glut in the talent pool