[getsat]

Frontrunning is definitely shady, but (from what I've read) only a small subset of HFT firms actually have the setup to do it. Those firms have custom FPGAs implementing the minimum amount of the Infiniband spec because anything else is too slow. They also pay a boatload to colocate their servers physically right next to the exchange backbones.

Most HFT is not frontrunning.

[joezydeco]

...but there apparently is enough of it where a 60 mSec advantage is worth the $1,500,000,000 investment.

[getsat]

Frontrunning isn't measured in milliseconds. It's microseconds (and soon nanoseconds).