walkman - 9:00 pm on May 7, 2011 (gmt 0)
I don't buy that Google can't handle frequent re-calculations. Maybe they can't do it daily or on the fly but sure can do it monthly or it makes no sense to go with that algo. A very slow to calculate algo in a fast changing field is useless.
This is penalty and it's deliberate. Unless Google sees your changes and removes the Panda penalty no amount of tinkering they do is going to help you much, at least not sitewide.
Question to ask: Will noindexing pages, currently supported by Google like tags and Adsense blocks were, come to bite people for another 6 months?