A Google Webmaster Help thread has one webmaster asking why Google isn't ranking his seven year old web site.
Google's John Mueller said that he is over doing it with the web site.
John explained that he is repeating the same keyword over and over again, to the point where it is making it hard for Google to "recognize what's really unique & compelling" on that specific site.
One of the difficulties our algorithms have with your pages is that they appear to be using the same keywords over and over again -- making it hard to recognize what's really unique & compelling on your site. For instance, looking at the cached version of your homepage: http://webcache.googleusercontent.com/search?q=cache:http://www.just-tow.co.uk/&strip=1 - I see over 1000 mentions of "towbar." The same is the case on URLs like http://www.just-tow.co.uk/towbars/honda-tow-bars/honda-civic-towbars.html (where even the URL includes 3 mentions of towbars). Our algorithms are pretty good at recognizing important content on your pages, you don't have to repeat them unnecessarily.
I know a lot of SEOs are obsessed with keyword density, even to this day. Maybe a post like this from Google will help relax some SEOs? Or maybe it will back fire and cause havoc where SEOs start making sure they don't mention the keyword they want to rank for at all on the page. ;-) Just kidding.
Forum discussion at Google Webmaster Help.
Image credit to BigStockPhoto for twins