In order to get the ball rolling, make it look like it isn't a ghost town etc. I've been offered a license to some pretty good content for my Q&A site, but it would be duplicate. Where is the line drawn between high quality but duplicate content that makes the site look active, and dropping in the search engine rankings as a result? I'm presuming it's not wholly inadvisable to do this.
If you're looking for search engine traffic this would not be a good way to go about for reasons that you already seem to be aware of. If you're looking to have content so users feel like your site is active then add this content to it but block it from the search engines via robots.txt or any exclusion mechanism.