The idea is that quality documents have a different co-occurrence of certain phrases (“money-words”) than spammy or low quality articles you bought for two dollars each from that low-quality writer in India recently who wasn’t even aware of how to use Word properly, not to speak about creating quality content…

Certainly a “SEOed” article around a phrase, let’s say “President of the united states” would use that term in all variations, word order and such.

A quality article really talking about the President of the united states would probably mention other “unimportant” things like names of past presidents, non-important things like amorous adventures, hollywood careers or other generally bad habits of those big guys that nobody would place an Adwords bid on for example.

The search engines just create a co-occurance matrix for all phrases in the document and match those statistics against other quality documents.

From the foregoing, the number of the related phrases present in a given document will be known. A normal, non-spam document will generally have a relatively limited number of related phrases, typically on the order of between 8 and 20, depending on the document collection. By contrast, a spam document will have an excessive number of related phrases, for example on the order of between 100 and 1000 related phrases. Thus, the present invention takes advantage of this discovery by identifying as spam documents those documents that have a statistically significant deviation in the number of related phrases relative to an expected number of related phrases for documents in the document collection.

So short – that patent and the wonderful clear exlpanation by Bill outlines pretty well, that Google & co DO have the means and technology to judge on content quality …

and that is the death for all SEO “copywriters” just focussing on keyword density, repetition and keyword stuffing.

What does that mean for you if you HIRE a writer for creating content?

DO NOT overdo your specifications concerning keyword phrases to use!

Especially in the last months I have seen content rank GREAT on Google (if on the right domains) for related phrases versus phrases that were really used in the content… you don’t need to have an exact mention of a keyword phrase for it to be found on Google anymore!

NO, it could even harm you nowadays – that’s the next phase of overoptimization penalties – create good, natural content and RANK!