I'm not saying everyone's got their algorithms tuned 100% properly, but the principle is sound. The Flash Crash should have been tempered by high frequency opportunistic buying (or by exiting short positions). Maybe the problem wasn't enough HFT.... The bottom line is that as long as there's transparency everyone sees the complete market conditions in real time. Reaction times might not be as fast for non HFT traders, but access to information is how the playing field really should be leveled anyway.
If an amateur is trying to clean up standing arbitrage opportunities in the face of HFT players they don't stand a chance and aren't playing to their strengths. Amateur traders should be looking to be the best at identifying mispriced stocks and derivatives and acting accordingly, or simply looking for the best growth instruments and hanging on (rebalancing and tweaking balance parameters frequently). The latter is my primary strategy because I don't have the time to commit to the former outside of some more long term macroeconomic plays.
The problem with dollar-cost-averaging is, well, it's like watching a 1500 player against an aggressive 2000 player....it's all too slow. And IMO, HFT's actually hurt the retail trader - bad. That's why May 6th happened....and WS was able to unwind some of those trades in that snafu ! Unbelievable. Are you kidding me ? Hey ding dong....you sold it to me.
The point is we're having problems leveling the playing field between the pros and amateurs. But then don't expect that to change.