Student visas are not limited like work visas (H-1B), and some are abusing the system by getting fake student visas to come to the US and work illegally.

This video was posted on IBNLive.com (India):

http://www.ibnlive.com/videos/44785/.html

and on YouTube:

http://www.youtube.com/watch?v=OHQZWIBT8QE