I was one of the webmasters that got b-slapped by the penguin update. I had a #1 site that didn't use any black hat or un-natural methods whatsoever but it went all the way down to who knows where and I don't think its coming back. Of course since it is a wordpress page it uses tags and each tag creates a page on the site i.e. site.com/keyword1, site.com/keyword2, etc and each one links to related posts for that tag. But inevitably some of those tags will display the same posts more than once and as a result you do have duplicate content showing up on different pages of the site. But this is part of the way Wordpress is structured and it has never been a problem before... but I am starting to believe that according to the way duplicate content is described by the Penguin update, this would be one of the things that could drop a website. Anyone else think this? If so, what are you going to do about it?
From what i understood, the penguin update penalizes auto blogs and everything that is understandable as Duplicate Content.
Category page and tag page may both cause duplicate content in your WordPress blog. That is why I always noindex these pages using All in One SEO plugin. You can do it too.
Jeffrey that is some excellent advice. I did 3 post-Penguin experiments on 3 groups of sites that were previously page 1 ranked for their main keywords. In one group I removed all tags, ALL of them... and to think this whole time I could have just did a 'noindex' and made my life easier. That said, it will still be interesting to see if this group yields the best results from the change. I can update this thread with results in a couple weeks for anyone that wants to see...or just PM me because this thread will most likely be long gone by then