[fpgeek]

My understanding is that the real leash is the H1B to green card process. The process is slow and complicated and switching companies often requires you to start over (not to mention opening doors for other problems).

[nine_k]

It's also rather expensive, and the sponsoring company paying (most of) the fees really helps.

[klipt]

Yeah, the green card process is hopelessly bureaucratic. Even an employee moving within the same company from San Francisco to Silicon Valley requires restarting the process from scratch.