Is there something that goes on with strike prices and huge OI. I notice that with the DEC 16 call it has a huge amount of OI compared to the other strikes and that some kind of barrier forms at that price that sort of keeps it from going up to 16+ I have noticed this lately with the ge calls I have been writing that have huge OI compared to the others.
It's a combination of delta hedging, gamma scalping, premium selling, premium buying and a positive feedback loop that continually attracts the attention and money of more and more traders.