Dup content issue

I have a site that's PR4 and its very similar to N4G.com. Basically members submit URLs and the popular articles get posted.

My problem is that many people (most) just copy and paste the first paragraph from the origin site and use that as the text on my site. I want to figure out the best way to display that text so I don't get a dup content penalty.

When a URL is reposted on my site, it links directly back to the originating URL (no nofollow). I don't think using the canonical tag would be useful for me as I would be sending all the PR juice away from my site, but would that help in not being penalized?

Is one paragraph even enough to cause a dup content penalty? Should I limit how much text a user can write with the idea of less text equals less dup content being the solution?

thanks in advance

 

lots of views, no replies. any opinions?

 

Play with the words?

 

Limit the amount of text. That's the only clear solution I see.

 

I think............. you should minimize similar content.

 

you should minimize the content and use the unique content for your website.