Back to school!!
TCS demands 50k for 2yrs, very bad policy, 1yr was ok, but 2yrs too much, this is from my offer letter which are same for every freshers everywhere in TCS.Yes as I said, generally Big Firms asks for Bonds to freshers. and the reason is already mentioned by RCuber.
As per asingh and others siggested, I'd personally suggest you to stay away from all these. At times they can become worse.
Join from SOHO / SME's to gain experience. Generally you'd learn better in SME's than these Big Firms.
But at the End of the Day, it's totally upto you. Though the 6month bond looks fine to me. As anyone would spend 1 year anyways in a company. But never think of handing over your originals.
But as asingh said, these are cheap policies companies do for hiring freshers, so that you don't leave right then after learning
PS : Keep away TCS from that list, they don't practise these type of bond policies, at least not here in Kolkata, for freshers too.