Month after month, year after year, duplicate content seems to be a HUGE issue. With no decent ways to detect it (that I know of), duplicate content can often go undetected causing problems for months. Almost every single client we take on has duplicate content issues, and often whilst they are client they make changes and cause more without us knowing.
Google needs to be more proactive about telling people when they have duplicate content on their site. Ok fair enough, it tells you if your title tags or meta descriptions are duplicated, but what about content? There are so many sites out there with duplicate content that don’t know about it, but if they did, they’d get it sorted. Google really needs to start reporting on this better – often people think they have been unfairly treated by Google, I’ve seen a couple in the last month or so – some of them have lead to Governments being lobbied.
If Google just made a simple change to Google Webmaster Tools to inform people of duplicate content, they would not only have less complaints, less people lobbying Governments etc. but it would also make their life easier, reducing the number of URL’s they have to crawl and helping them improve quality across the board quite easily.
So come on Google, sort it out, PLEASE!