The big Banks and Governments will use fear and human psychology to scare people away from crypto currencies, they will make it so volatile that most people (non-traders) cannot handle it.
Crypto-currency has always been volatile
Good point.
I guess the human psychology of greed and fear will operate with or without HFT (high frequency trading), but manipulation might help push the fear or greed a notch further.
Crypto-currency markets though are never dull though.

Wild swings.