CME Initial/Maintenance Margin Ratio Change

• Received this CME notice after last night's NY close, effective Friday 04Nov11. First time I have seen such a change in my 6 T4L years.
• On a single contract micro level, when one opens a position, one has to put up IMR to the exchange. Maintenance margin is typically set at around 80% of the IMR. If the position moves against you and the end of day MTM position value falls below MM, then you need to top up additional margin back to the original IMR level the next day.
• In practice, the margin call is based on overall MTM across one's account. For me as an individual trader, my total IMR is usually no more than 25% of my account equity ie always plenty of excess funds parked at MF Global (in reality, the decision is made the other way - ie decide how much I can afford as risk capital, put that into a margin account, and then size overall open risk to no more than 25% of that at any one time). Need to change this practice for my next broker.
• For financial institutions, it is a lot more protective in either direction, ie daily sweeping out of excess funds and paying in of margin calls is a way of life, rather than the extraordinary for private investors like me.
• Interesting to see how large an impact this CME raising of MM to IMR level will have on markets on Monday. But what I would really like to know is the reason behind this change now, in the middle of MF Global bankruptcy. Am pretty sure the former is partly as a result of some untoward discovery in the latter's practices. Any insights?