When search was a baby, you could rank high by just adding white words. Those are words with a tiny white font, so the readers wouldn't see them, but the search engine would. Then the search engines figured it out, next…
Roll a few years later. Why bother creating content? Somebody else can do it for you. That's the area of user generated content with blogs and comments. The problem with the blogs and the comments is that the vast majority of the blogs are just “junk”.
All the announcements are all the same. They basically copy each other, just changing the title to be more provocative, like "Canon Sucks" or "Nikon Sucks". The goal is to inflame the readers, piss them off, and they will comment on that web site. These articles are just a few lines long. They not an exact copy of each other but they fit the definition of plagiarism. They are close imitations of each others. They would usually rank pretty high, because of the regular fresh content.
Google was ranking each web site as a separate web site. In the last week of January 2011, Google changed its tune. Matt Cutts of Google aka the top banana of the anti-spam department at Google or Quality Control has put in place a new “filter” that lowers the ranking of these websites.
According to Matt Cutts, 1% of all the websites are significantly affected by the new ranking algorithm. Those are website that used to be on page 1 and now are dropped somewhere in the bowels of the search pages.
The other group of web owners affected by the change are the “pirates”. They are the one that steal your content. Just copy your web site with a “scrap engine” and use it on their web sites. It's the first time that they are getting severely penalized.
Original content “rules the roost!”