What if i copy small excerpt text from a site with a proper link back to that site like rss feed ? Will google also treat that duplicate content?
You will not see the effect if it is only one. It is just like similarity of Phrases but if you do it more than enough then for sure you will be penalize
I will suggest to not do such thing. The content is already present in other sites and showing it in your site will bring no good as it is already found by Google at other sites. Try to add useful/unique content in your site. google.com/support/webmasters/bin/answer.py?answer=66361
As long as you have a large amount of unique contents within that page you can have a excerpt or two.
I would also not prefer for you to opt this suggestion. Couple of times, I had seen my own content with my blog link posted in that copied content, but alias within a week or so, the page was dumped by google. Thanks to their fantastic startegies. Please do not copy the content, friends.....
There is no such thing as "duplicate content" in the context of what you are doing. As long as you do not infringe on copyright laws. It is perfectly legal and appropriate to quote others. It's done every day on millions of reputable, authority blogs. Bompa
If you have a reason to copy and paste the content onto your site, while providing a link to the original source for credit, there's no danger. Just don't expect that page to rank higher than the original source. As long as it's not your main strategy for building content I don't see any problem.
We don't have control to our content once it get live on the internet. We can't stop others from copying your content.