John_Webster - 8:50 am on May 2, 2010 (gmt 0)
This issue of reduced pages indexed is not new. I've observed it after Universal, Big Daddy, Jagger, etc. About 3 - 6 months later numbers of pages indexed are back to normal and so are SE referrals.
My theory is that Google uses these updates to spring clean its index. Can you imagine the incredible cost of indexing the billions of pages of duplicate content, abandoned shopping carts and all the other cyberjunk?
The problem is that it is the most effectively SEOed sites that suffer the biggest drop in SE referrals at these times.
Being at the mercy of Google is a hell of a way to run a business.
You also need a hell of a good relationship with a client when all you can say is "be patient it will come back, trust me". I have not found anything that I can do to change the Google status quo. I just keep the client's SEO programming going as if nothing has changed. So far, it has worked every time.