I do think that the fact that many people often scream manipulation whenever the price of bitcoin falls is a sign that bitcoin does need a small amount of regulation to make sure everyone has a level playing field.
I disagree. The bulk of the screams for manipulation are built on poor reasoning, a weak understanding of volatility and probability, and a cognative bias which attributes anything interesting as having come from some thinking agent (see the intellegent design argument). This is not new to the community and indeed was more pernicious in the past with the whole "the manipulator" meme.
I'd say nothing needs to be done about this but if the screams are worrying, I'd recommend addressing the actual problem: the demons in peoples' minds. At the very least, let us spend our energy advertising Bitcoin to professional day-traders, highlighting how some actors are pushing the price around in predictable ways. Such "manipulators" are easy prey for a seasoned trader and these traders will help to reduce volatility and bring about swift price discovery. They may even help to drive the amateur speculators and gamblers out of the market (good riddance) leading to even lower volatility.
Regulations will only make things worse as they will certainly raise the barrier to entry for new traders and/or trading platforms and may even make truly decentralised trading systems effectively illegal. Less choice will only foster abuse and lead to a less level playing field. The greater costs which must come with regulation would also be most unwelcome.
is just a win-win situation. 
