How Do You Avoid Building A Content Farm?

Matt Cutts of Google's webspam team recently wrote a Google blog article about content farms, and in the process provided some insight into what is a content farm.

In Matt Cutts' post he wrote:

“content farms,” which are sites with shallow or low-quality content. And "sites that copy others’ content and sites with low levels of original content."

Looking around the web I see a number of websites that aggregate content but the content on those sites is of good quality.

Sometimes those sites repost duplicated content from other sites.

zdnet.com comes to mind, where nonpaid authors write columns and reproduce articles from their sites or blogs.

When I worked at Forrester Research as Online Community Manager I helped set up the feed from one or two of the Forrester blogs, where a post would be published on the Forrester blog and reposted on ZDnet. Now isn't that duplicate content, even if it's high quality?

There's Social Media Today, one of the leading sites on social media marketing, virtually all of the blog posts are duplicate copies of writer's posts on their own sites. Though writers are required to write unique posts four times a year on the site. Here you have an important community site, but most of the content is actually duplicated.

Again in Matt Cutts' post he wrote:

“content farms,” which are sites with shallow or low-quality content.
sites that copy others’ content and sites with low levels of original content.

Given Matt's definition, doesn't that put ZDNet and Social Media Today into the content farm category, or are there other factors at work here? Would be helpful to get answers from the community or even Google.