That isn't really an example of market manipulation. Market manipulation is an intentional manipulation of the market. (http://en.wikipedia.org/wiki/Market_manipulation) The Knight Capital incident was an example of a firm performing bad trades due to an error in their systems. Their behavior certainly wasn't intentional or profitable.

HFT isn't based on market manipulation. Some HFT firms perform market manipulation, as do some non HFT firms, but this practice is illegal. (For example, newedge was recently fined for market manipulation)

The Knight Capital incident isn't unique to HFT firms - any firm that does automated trading can fall foul of similar problems.

It can even happen to manual traders. If you accidentally screw up and run the wrong strategy (e.g. buying Tweeter Inc. when you intended to buy Twitter), you'll very rapidly lose gigantic piles of money.

Losing your money in the stock market != market manipulation.

Yeah, but the "HF" part of "HFT" tends to make an elephant out of a fly.