Also see: https://blogs.wsj.com/digits/2016/03/17/study-immigrants-fou...
I was recently speaking with Demis Hassabis and he recommended looking for startup funding in California but continuing to work out of London. More and more companies are gravitating towards this general template (not London specifically). Would you rather have some low level Stack Developer working at Airbnb on an H1B build the next Billion dollar startup in the Bay Area or out of Bangalore?
Yes, hiring someone with an H1B might cost a company 10k less per annum. But what would it cost America to not have these foreign workers want to work in California altogether? Besides, it isn't fair to build such an impressive hotbed of thought and progress and then try and wall others out of it.