This is untrue. If you actually look at the data, you'll find that the companies who hire the majority of H-1Bs are actually not the silicon valley usual suspects. Some of them you haven't even heard of.
If you're not in the consulting world or are not a foreign worker in the US, you probably don't know much about Infosys, Wipro, Tata consulting services, Satyam computer services, Larsen & Toubro, HCL. Yet these companies comprise the vast majority of all H-1B petitions, with average salaries ranging from 50k to the 75k, well under market for tech.
Some silicon valley firms are there, yes. IBM averages 82k, not bad for a company which capitalizes on commoditizing engineering. Then there is Microsoft, Oracle, Apple, Google, Amazon, Intel, which form a minority of petitions, and have /average/ salaries of over $100k. How is that not a competitive salary? 6 digits is not wage slavery, and these people were not compelled to settle for that, for christ's sake.
The companies have to pay 5 to 7k in legal costs and fees to get the H-1B, and even more for larger companies. And they have to wait for months for a chance to get it approved. For the former group, given how low the wages are, this is cost effective. For the latter group, it really isn't better.
Facebook, which doesn't even make the top 50 list, has been campaigning for immigration reform and has repeatedly been the target of "taking our jerbs" rhetoric, when their average foreign worker salary is around 120k.
So yes, some companies win, but not the ones you expect. Blame the right companies, and don't throw everyone under the bus.
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Data: http://www.myvisajobs.com/Reports/2013-H1B-Visa-Sponsor.aspx (yes, yes, not all LCA's files actually turn into visas, etc, but they are representative of wages companies intend to pay.)
Disclaimer: I'm on an H-1B, and I'm getting a bit sick and tired of clearing up misconceptions that keep coming up on this subject on HN. An old post on the subject: https://news.ycombinator.com/item?id=5515519
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edit: To clarify, yes, I think the legal immigration process, especially the H-1B is messed up. I think it needs to be fixed and modernized. I think it needs to be untied from company sponsorship, and the workers need to not be tied down to companies, and subject to market forces. I think there needs to be more transparency too in terms of the data. I've even proposed a policy limiting the number of H-1B workers larger companies can have, which addresses the H-1B sweatshop issue somewhat, while not damaging foreign workers. But yeah, I get mad when people talk about a subject so important to me without having any clue about the data, and reach their conclusions through political rhetoric they heard elsewhere.