I want to create some web 2.0 properties for my site but my question is that unique content is necessary for all web 2.0 site,I want to create more then 20+ web 2.0 for my web and if Web 2.0 have duplicate content does it effect my ranking ? Thanks
You definitely want your articles to be as unique as possible. Be sure to change your headlines and I use a simple program like WordFlood 2.0 to make each article unique for those particular projects.
As Oranges said. You can use them effective if they are not too much similarity. It would better if you can create a short unique description for each title you submitted on your own 2.0 instead of using a part of content page on it.
I would personally spin articles for each Web 2.0 site. If you manage to create uniques articles for each of them, you can have each of them get indexed seperatly. So, try to change them a bit, like few sentences, titles etc.
Well beat way is put unique and fresh content on the site coz when Search engines crawl some new food then it would get weightage to your site. But you can make your content spin, remove similarity from the stuff and try to put at least 50 to 60 uniqueness in your content then it would not create trouble.
In my opinion, you would be better off researching your subject thoroughly, making the best Web 2.0 pages you can, and then paying someone $5 to rewrite them a few times instead of spinning your content. Spun content is really only useful if you're rewriting 1000+ word articles for 100 or so properties. (But then again, that is just my opinion. )