I'm thinking about opening a new site, or offering a few free blogs on my site using wordpress and I was wondering. If you have blogs on your domain and 2 people post the same content or very similar content, will the search engines punish your listings? and treat them as duplicate content. And would having a variety of themes help? thanks for the help.
If two pages have substantially the same content then it might meet the duplicate content criteria but that just means that only one of the results will be displayed in the SERPs. There's no penalty for duplicate content as there are legitimate uses for this such as article syndication but google tries to find the authoritative page and displays that in the results. Having a variety of unrelated themes on one site will make it hard for SEs to determine what your site is about if you have no main theme. If you do have a main theme then the unrelated material will probably dilute your main theme making your site less relevant for that theme. This would make it harder to rank for anything but I'm not sure how your site is set up.