It might be helpful to explain in plain language what you mean by increasing liquidity. As I understand it, marginal spread reductions only marginally improve your ability to sell at or near a particular price, and they provide no benefit to you if no one is buying near your sell price, or if there aren't enough buyers available overall.

But it would be interesting to see some quantitative data on the effect.

Increasing volatility and enabling fast algorithmic trading may not be good things overall, even if some traders benefit.

And as I noted, if you care about fairness in an online game, usually you try to remove the penalty effects from long ping times (or the bonus effects from short ping.)

That's a bad thing. When transaction costs were high the market didn't own society as much.