No one is going to manipulate the market. I am assuming a certain amount of honor here.
Then who needs escrow? Unless you are very close to someone, it is foolish to expect them to behave to a standard of your mind. One is rarely well advised to assume even that an internet counterparty intends to hold to their commitments, and insane to expect them to hold to restraints to which they have not agreed. Honor is highly idiosyncratic, above and beyond being cultural, and extreme diversity of idiom and culture is to be expected in a global community.
Certainly you could easily drive the market to 435, in a matter of a few minutes work. Would it even be manipulation if you had intended to put on a big short anyhow?
Manipulation is easy to see. For instance, the markets are following Houbi. If they act out of accord with Houbi all of a sudden with a big dump or buy, then its pretty obvious. Rpeitila cares about his reputation. A LOT. So much so, that I don't think he would openly cheat in this case.
As for me, I am a long term bull. It would be a huge risk to short that many BTC. I'd have to wire addition funds onto the market, as I am pretty much full fiat at the moment. In fact, I have buy orders in right now, not sell orders.
Im positioned against my own bet at the moment. And I would not change those, because I believe they will get filled on the way to 435.