[cowmoo]

You are right that for a individual investor focused on the long term, a algo-order probably wouldn't make a difference in comparison to a market order with your E-Trade/Schwab account (most likely, your order-flow won't go directly to the market anyways; it is either crossed internally, or re-routed to a broker/dealer that's paying retail brokers for the order flow such as Timberhill).

However, I respectfully disagree that humans are better at making trading decisions than computers. The world of algo trading can be divided into two sides, a) high frequency traders, who through fast cancel-and-replace limit orders and colo with the market centers, try to act as virtual market-makers (or scalpers, depending on your perspective), b) buy-side institutional fund managers who want to complete their orders, without HFT predators and negative market pressure. Large block orders are spliced into small lots (i.e., VWAP) and sent to the market using intentional limit price over time to hide the movement of a huge buy or sell order on the market.

Human beings might be better than machines at picking single stocks for long term investing (although most people are probably still better off investing in an ETF). But that's not how sell-side traders make money in the first place. Guys like GS/MS/Timberhill make money by having the unfair advantage of faster execution speed, more capital and specialized trading algo's against the small retail investors.

[aspiringsensei]

Has there been a good writeup of what HFT "Is" at any point?

What is your impression of them as a pernicious/positive force? Are they essentially market making?

This is the kind of stuff I really should have an opinion about, but I haven't found anything to lean on in the public domain.

[cowmoo]

Has there been a good writeup of what HFT "Is" at any point?

http://vimeo.com/6056298

What is your impression of them as a pernicious/positive force? Are they essentially market making?

Open for debate. Depends on what you mean as a pernicious/positive force. Good for retail investors, institutional investors, stability of the market, or the sell-side? All of these are conflicting sides. It is generally SEC's mission to protect the small individual investors' fair access to the market, while trying to walk the fine line of not disrupting the big institutional investors/sell-side brokers' way of doing business (and their political lobbying groups).

Pro HFT argument: HFT are virtual market makers that through the use of technology and arbitraging through multiple ECNs, are decreasing the bid/ask spread of the traditional market makers and providing more liquidity to the market. They serve as stabilizing force during irrational exuberances.

Con HFT argument: HFT are bad predators who through technology, jump ahead of institutional investors' block orders and in term pass on higher priced liquidity to retail investors that no one needs. They don't serve as stabilizing force, as they stop trading as soon as they stop making money and in fact may fan the fire by employing high frequency short selling in a flash crash.