On the aftermath of the May 6 Flash Crash, many exchanges decided to break trades, but the process by which they deemed which trades to break was criticized roundly. Roughly 21,000 trades were broken--leading to relief and anger depending on what side of the trade you were on--with the criteria being how far away the trades were from fair value.

To make the breaking process less arbitrary, the exchanges have come up with formulas to govern this and provide some certainty.

Exchanges will stop trading in stocks that trip circuit breakers. If prices deviate from the so-called "Trading Pause Trigger Price" by a set percentage--either 10 percent, 5 percent or 3 percent, depending on the price of the security--the trade will be broken.

As explained by Traders, trades not governed by circuit breakers will be broken if they deviate 30 percent from a given reference price.

The approach is seen by some as a step up from what exists now. But others wonder if the method needs to be refined, especially when it comes to securities like ETFs that are not subject to circuit breakers. Perhaps the percentages and triggers need to be re-thought. And perhaps the rules for stocks and ETFs need to be harmonized. There are many tweaks to be made. Still, anything that provides objective benchmarks will likely be a good move.

Getco, however, suggests a different approach. Instead of breaking trades, why not just adjust the price of questionable trades. Such an "adjust only" policy would serve to reduce instances of widespread position uncertainty," Getco argued.

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