4th reason why prices may be manipulated is that its a free world with no regulation, no checks, no accountability. If the game is open to being rigged, there will be people ready to profit from that opportunity.
I am also bullish because banks are getting involved and that may be the likely cause of this. Shake the weak hands and accumulate as much as possible. I do think negative or sideways action will continue till regulation establishes btc as a commmodity. Or some regulatory approval is in place for institutions to jump in.