For those that are worried about duplicate content issues and getting penalized for them this information might serve useful to you. There is a thread on SEW forums detailing a situation where one of the members had several pages 302 redirected to pages on his site. This caused problems for Google. Fathom, a member on SEW forums posts information about duplicate penalty timeframes for offenses based on first, second and third time offenses. He mentions that:
A dup penalty timespan is based on your offense.
1st Offense: 30 days
2nd Offense: 60 days
3rd Offense: 90 days
So 'if' [for example] you had a 1st Offense and change something and Google detected that and then later found other dup content - you would go to a 2nd Offense timespan.
I emailed fathom to get some verification on where he obtained this information. He posted back in the forums that Matt Cutts of Google at a recent WMW PubCon mentioned it.