From a systems point of view, there's a lot of uncertainty over the current rules regarding short selling. The bottom line is that rule tinkering often results in required system tweaks, which can be expensive. Case in point: The recent short selling ban initially imposed on 800 stocks. When it comes to the recent attempt to throttle back naked short selling, it looks like the penalties imposed on firms that built up large, fail-to-deliver positions are working, notes Traders. Given the current climate, many anticipate additional regulations, something like the old uptick rule, or some kind of price test or circuit breakers. This will result in some additional system work most likely, so get ready.  

For more:
- here's the TradersMagazine.com article

Related Articles:
Short selling ban tests Wall Street systems
List of banned short-sale stocks
Are the shorts really to blame?
Stocks safe from short sellers