Take a look at Joe Saluzzi's rants / articles / interviews. He's from Themis Trading in NJ, and he's been highly critical of HFT for a while on CNBC, Bloomberg, etc.
His view is that HFT creates the illusion of liquidity, while making the bigger market participants pay for it via larger slippage on entries and exits as the HFT detects buy and sell orders and front runs them, all the while presenting the theory that it is generating liquidity. Thats why dark pools got so popular with the bigger traders, is because of HFT.
The naive user of a trading system or discretionary trader may discover that the 10 million shares traded on a stock per day are only traded amongst other HFT players, or different versions of their own HFT strategy, and that when they want to put in a 500,000 share sell order, they end up driving the stock down 5%. Here, HFT are not exactly creating liquidity....
So you might call this liquidity arbitrage- fooling people into thinking that its liquid, when its not at all. HFT as a rule has also abandoned small caps, and moved to large cap stocks exclusively, creating a big hole for small caps.
HFT also do latency arbitrage- say they have a 50 millisecond connection the the exchange, whereas someone else has a 200 millisecond connection by the time their old VB system triggers a buy/sell order, the HFT has already got in front of it. And as decimal based trading picks up.. HFT makes money here as well.