In the last three places (including my current employer) there were huge swaths of H1-B's from India. After some long lunches and happy hours, I found out that a) they're being paid significantly less than I was and b) two of the three companies wouldn't sponsor them to stay at the company and come on as an FTE.
This meant several trips and back and forth between the states and Bangalore to get a new visa, then turn around and try and find a new gig somewhere. For the developers who were single it wasn't a problem. Those workers with families, it was quite stressful to have their families moving back and forth on a regular basis and not having the stability of knowing they had a gig lined up or not.
Toss in the fact getting these visa's are incredibly competitive and I can only imagine the stress involved.