NSE has changed the Nifty strike prices to be 50 points between strikes, rather than the 100 points it is now. In a circular, the new strikes will magically appear after August 30, 2013.
Given the liquidity in the Nifty, it makes sense to have strikes at 1% intervals; Nifty options at a 100 apart leave too little value in trading spreads.
I remember when trading such options were commonplace, until new rules came in and widened the distance between strikes to 100. Of course, if the Nifty were to drop all the way to 4,000 this would make even more sense; but that is a little too far a drop to happen. Or, given recent events, is it?