I'm not a trading expert but I guess smarter and richer people/entities will probably also run bots and a whole lot more complex trade monitoring and market mak

I'm not a trading expert but I guess smarter and richer people/entities will probably also run bots and a whole lot more complex trade monitoring and market making strategies or algorithms. In your example, somebody interested in keeping the price at or above a certain level and that has a couple of million to waste on that could potentially place a 900btc buy wall as soon as you managed to market sell the first 100 of your 1000 and so you'd sell the rest into the wall and not move the price as much as you'd wish. And market psychology is a strange thing that could actually even make the price move in the other direction as thousands of traders would see the huge buy wall and assume the price could only go up and therefore buy more to go long which would increase the price even more. If that or similar happens then your "shorting at X while dumping at Y" strategy won't be as successful as you would expect and you might just end up dumping your 1000 btc at mostly the same price. 1000 btc is a lot of money for most people but not that much on a daily bitcoin trading day. Even the 1 billion dollars in bitcoin isn't really capable of damaging the market all that much as most alarmist articles made it seem once this transaction got noticed imho. Remember that there are/will be about 21 million bitcoins. I'd say its safe to assume that whatever "big idea" one has to manipulate trading or financial markets has already been thought of, implemented, tried and failed or succeeded to some varying degrees, especially on deregulated crypto markets.