That is just his point of view. He is not the only one controlling it, He think he have a lot. It didnt even moved that much what bitcoin price is, It is still there 380-450. Say what he want but I dont really believe him. We have our own opinions.
But people are scared of what his opinion about bitcoin, he is one of senior developer of bitcoin so his though can effect bitcoin.
The only thing this whole commotion does show, is the 'immaturity' of bitcoin/bitcoin community. Not saying that that is a bad thing, a lot of things are still possible to improve bitcoin as a stable means of payment, BUT there will always be more speculation than certainty considering the price or even the survival in general of bitcoin. As I am sure (my opinion) that bitcoin will never die (atleast not in my lifespan), I am also sure that this kind of payment system will always remain a bit 'immature' compared to USD/EUR/...
As this system makes it possible to stay completely anonymous, to make complete anonymous transactions, it will always remain somewhat in a 'dark' corner of society. Because, let's be honest, when you want a payment system to be completely anonymous, there are some things you want to be kept private. Otherwise you would not even think of coming up with something like bitcoin (do correct me if I'm wrong).
But well, all this discussion is in fact just speculation aswell. If tomorrow WW3 commences (if it has not already), what will happen then? Don't think bitcoin will be a profitable means of payment when nobody has got a way to access them. And I know, if ... if... if ...
It is a fact that alot of criminal activity goes along with anonymous payments, but would that be a reason to banish bitcoin? The criminal activities would just adopt, as they always will. As long as there are people profiting of these activities, there will be means to make them possible.
As for Mike Hearn's statement, everyone has a right to his own opinion, and as you said, if one of the senior developers publicly claims to have lost trust in 'his' system, then it is normal for people to start wondering or even panicking (immaturity, once again) about the investment(s) they made. But as with everything in life, profit and risk go hand in hand, so if youre not willing to risk any of your preciously earned money, then put them in your safebox at home. No money is ever truly safe. You just have to make out for yourself whether the risks are worth the (possible) earnings.
We'll see where this goes, and I think the next milestones that will happen are the following: increase of blocksize, and the halving of mining revenue. Not sure when these will happen exactly (and too lazy to check atm) but I do think we will have gone through some decent price changes in 4-6 months from now when these events have passed.
Nobody can force anyone to believe or vouch for anything other than he would like himself, but I am sticking to the bitcoin society for a while (I am still quiet the noob at the moment in the btc world so I too will have to see what will or will not happen). But I do like the idea behind bitcoin. And in the end, that's what counts, no?