Yes! Right now I am posting the same post to many blogs and yes, the posts are identical - this is the same as posting the same article to lots or websites and many more promotional strategis happening out there.
Now, one of the blogs today keeps scoring quite high and that's the only blog that scores differently today.
While all other blogs except a couple do't show up much in the stats.
So, yes... It could very well be that the search engine picks up one post, indexes it and then considers all the other posts as duplicated content.
What about videos for instance?
I post my videos to 15 different sites but many do show up in the results side by side.
Simple... because the actual page + title of the pagewhere the video appears has no similarity with that from another site.
In other terms, it does not trigger duplictaed content.
That could be a key answer and something to follow up.
To follow up absolutely... I need to fully understand how search engines index my posts and identify drop or raize patterns.