SEOPTI - 11:21 pm on Mar 15, 2010 (gmt 0)
Old news, this has been going on since September 2009, in WMT usually you can see low crawling volume for your sites.
The URLs where there is less crawling/indexing drop from the index if a URL has not been reindexed within 2-3 months. If this is the case, the cache date disappears next to the URL first and then the whole URL will be removed.
Definitely overall a shrinking Google index.