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Now wouldn't it be in your best interest to sandbox your competition? You see a new site throwing up some PPC ads in your space, you immediately give them a few run-of-site links from some other sites you run and watch them get sandboxed.
Maybe unethical, but seemingly a solid approach for anyone in a competitive industry.
Oddly enough Google has had a mini shuffle sometime today as I have just checked and I'm now in pole position for my keyword with the big bank subsidiary down in second spot.
Although a single keyword covers 90% of all searches there are some other minor phrases that are sometimes used and I do have other pages optimised for those keyword phrases. My site ranks quite well for some of them and poorly for others so I need to keep working at it.
I am always amazed at what people put into search boxes. In all the sectors we cover, probably 10% of traffic comes from the obvious search phrases which we have researched, while the rest (which is still relevant) comes from unpredicted search phrases.
When you say "some other minor phrases" what you may be seeing is a tip of a huge iceberg of minor phrases that you happen to catch. Increase your content around the topic and you could start catching 10 times more traffic making your major keywords far less important.