Blogost – googlewebmastercentral
http://googlewebmastercentral.blogspot.com/2008/09/dynamic-urls-vs-static-urls.html

URL-Rewrite

Question:
Should I try to make my dynamic URLs look static?

Google Answer :
It’s much safer to serve us the original dynamic URL and let us handle the problem of detecting and avoiding problematic parameters.

Question:
Does that mean I should avoid rewriting dynamic URLs at all?

Answer Google:
That’s our recommendation,

………..
more:

to produce static-looking URLs from a dynamic site, you could be doing harm rather than good:

Hi 😉 just look at the domain on which this was posted:
http://googlewebmastercentral.blogspot.com/2008/09/dynamic-urls-vs-static-urls.html

So maybe the google guys will go on with drinking wine and just the SEOs should drink water in future ;-).