David Naylor posts about how to prevent Google’s newish duplicate content filter issues from hurting WordPress blogs:

first what you need to do is get rid of those Urls that look like this:
http://www.mattcutts.com/blog/?p=16 and replace them with
http://www.mattcutts.com/blog/up-up-up-up-up/ .. but Matt.. what you must do is have a robots.txt .. in that robots. txt file add this little line in ..

User-agent: *
Disallow: /?p

If you already have a bunch of links into the ?p pages then you would probably need to do other things as well, but if your blog is fairly new it is fairly straightforward and a good call to block search engines from accessing the ?p pages.

Some related threads about Google Washing:

• Threadwatch
• WebmasterWorld
• Dark SEO Team (responsible for Google Washing Matt Cutts blog)