I have little to add on the substance other than to note that I find these posts (and the discussions here) incredibly informative. They shed light on an area that turns out to be far more interesting than I would have imagined.
However, the last example may be more realistic than you suppose. DEF CON last year contained a presentation[1] on security considerations in HFT networks, which I attended. It's thought-provoking and something I hope gets a little more attention.