>> It is simply not credible that someone would put on a huge position in 2008 and not give any thought to the impact their own trading would have on prices.
Good point, it is surprising this keeps happening. There was difference, though. The London Whale got too big for his market, but I don't recall him ever suggesting that he hadn't even considered the effect his own trading would have on prices.
And yet it keeps happenning, see "London Whale": https://en.wikipedia.org/wiki/2012_JPMorgan_Chase_trading_lo...