True. Each side has their own set of advantages/disadvantages. And so you'd have to adapt and take that into consideration in addition to bid/ask spread. It's not impossible (nothing is impossible), and you'd only get killed by brokerage fees if you're overtrading.

If you can find an algorithm that can trade only a few times a day and ride stocks that has a volatility of 1% or more then even at retail commission levels you can still do pretty well as you slowly build up your account to trade strategies that require more churn.