Great post and good question. This part caught my eye:
[SEC Commissioner Annette Nazareth said ending the grandfather protections won't have adverse effects, such as volatile trading, that prompted the SEC to adopt the shield in 2004. SEC Commissioner Kathleen Casey also endorsed the change, saying the benefit of doing so more than offsets concerns that a " squeeze" on outstanding short positions might roil stock markets.
To shed light on delivery failures, the SEC plans to make aggregate Depository Trust Co. data available on the SEC Web site shortly, after removing certain confidential information from the data feed already supplied to regulators by the DTC. Agency staffers said providing hard data on delivery failures may reduce the number of requests the SEC has received for such data under the Freedom of Information Act.]