I don't think that negative interest rates are viable for the major banks. That will destroy their short term holdings, as people would rather keep money in their hands or in the form of bonds, FD.etc.
No , they won't
An ""experiment" already happened in Denmark and nothing really happened , no disaster but also no real recovery:
In July 2012, the National Bank of Denmark imposed a negative rate of minus 0.2 percent on bank deposits stored at the central bank.
Contrary to some fears, the move did not create chaos in financial markets or cause bank computers to crash as they struggled to process data for which they were never programmed. The Danish central bank issued plenty of warnings that a negative rate was on the way, giving banks time to prepare. The E.C.B. has sent its own signals that it intends to make such move.
“Zero is just a number,” Mr. Rasmussen said. “The world goes on.”
http://www.nytimes.com/2014/06/04/business/international/european-central-bank-chief-looks-for-silver-bullet.html?src=rechp