"I was watching Bloomberg/CNBC the other day and someone mentioned the "cross of death" - a term used when the 50-day moving average breaks down through the 200 day moving average on the S&P. This they said is a very negative signal for the markets. Any views on whether such an indicator does have any value?"

David Fuller's view Obviously it is not a good sign. However it is telling us what we already knew.

Ever since that 10-week rally peaked in April, the technical action has been deteriorating, aside from a 2-week rebound in mid-June, which was wiped out last week for a number of stock markets. Today, there is still no evidence that this outsized correction is ending although the latest decline is becoming overextended. The next obvious psychological target is 1000.