The dangers of high frequency trading...

I am becoming increasingly convinced that high frequency trading represents a significant de-stabilizing influence on stock markets.  I do not buy the idea that high frequency trading strategies simply improve informational efficiency in the markets (by eliminating minute price differentials between buyers and sellers) and provide extra liquidity to the market when it is needed.  I happen to think that these high-frequency trading algorithms and electronic trading strategies destabilize the market.  How? I have no firm idea.  Just the intuition that such strategies increase the frequency and density of interactions between market participants and that perhaps this is not a good thing...also it may be the case that by driving down buy-sell spreads HFTs force institutional investors to pursue other more risky strategies to make higher returns (i.e., mutual funds, pension funds, etc may increase their leveraged positions in order to compete with HFTs or something similar).   

Here is the link to the SEC report on the "flash crash" that took place in May 2010. The report details how the interaction between high-frequency trading algorithms and electronic trading strategies implemented by structural traders (i.e., a particular mutual fund complex) where main causes of the flash crash.  Here are some links to recent articles and blog posts that go into more detail on the issue.