I just did a search the other day on this and Google is not penalizing for duplicate content per say. I think that there is a Matt Cutts video on duplicate content for websites. It would kind of suck since if you offered a training class that is offered by say the Red Cross and you offer their class on you site as an instructor to be penalized for this.
ive seen pages getting de-indexed. nd if its bcoz of dynamic urls then can lead to split pagerank issue.
one of my sites keeps 3 copies of same sites under one domain... This is due to country variation preference... I don't see any impact...
I don't think that duplicate content will create much problem untill and unless it is done repeatedly. However, prevention is better than cure but, no one knows when a small mistake can penalize you by Google.
While Adsense, a program of google does not take kindly to duplicate content, I am not sure about the approach of its search engine. It is not known to de-index the site for sure, but I am yet to assess myself whether it does affect the serps badly. I do not think it matters much to its PR ranking ..though! Regards, RightMan
as lindamood1 said its effecting on ranking ... will kick from google SE.. and coming back after remove the duplication is alos very hard...