What if I break the company bond? What role does NASSCOM play?

Most freshers who have secured a job in an IT company through campus placements are worried about the Employment Service bond that they are made to sign. The 'bond' - which is essentially a contract that demands that you pay a certain amount of money if you choose to decide to leave the company before a specified time - has been made mandatory by many IT companies including TCS, Infosys, Tech Mahindra, Wipro etc. in the recent past.

Someone just sent me a message asking, "What would happen if I break the company bond?"
He further wrote, "Will I really have to pay the bond? What if I refuse stating some reason?"

It turns out that news has it that such bonds are illegal in India, in that companies can not force any employee to sign a bond. Only how much of it is true nobody seems to know.

Some also say that NASSCOM can blacklist an individual if he/she resigns from a company without paying the bond amount.

Some say it is a a myth that ITES companies can blacklist you on NASSCOM.

I've heard that there are thousands who simply walk out of companies and never pay the bond amount. Some say that they receive a legal notice, but they don't pay heed to it and all of it dies within a few months.

I read somewhere that as per the Indian Constitution, "No company bond can force any person to work against the employees wishes."

So, what is your say folks, how serious are these IT company bonds? Share your experiences please.