zerillos - 9:34 am on Feb 3, 2011 (gmt 0)
the 301 works only to a certain point. I recently messed around with putting a mobile version of my website. Because of my incompetence, googlebot (and not googlebot mobile) got to spidering the mobile content, which resulted in my whole site getting duplicate content. This just took less than 48 hours!
I pulled out the mobile content and 301 all the pages to their desktop versions. After 24 hours, around 80% of the duplicate content was out of the index. This happened around 3 month ago, and there are still around 10% of those pages in the index.