The only "violation" I know these companies do is that they make the employee sign a bond that they have to come back to India and give a 3 months notice period if they want to resign while in US. And this is not just Indian companies. I was surprised to learn recently that the Indian division of an American product company (top 1 or 2 in the world in what they do) has a 12 months notice period with around 10 lakh rupees bond. Compared to that, Indian companies are less evil.
Another thing the Indian companies do is make you work on less desirable projects or otherwise you have to go back to India. And they don't treat their employees the same way a product company in America would do. They see us more or less as "you should be grateful to us that we gave you chance to come to US".
