This is based on a page on seomoz.org. They conducted experiments on websites and found that if you have more than one link to Page B from Page A, Google counts only the first link as relevant. And the anchor text of the first link is considered for ranking of Page B.
For example, you might have a link called Services on the top nav of your home page, and another link called Call Center Services inside the page, both linking to your main service page which talks about all your services. Google gives weightage only to the first anchor text “Services” while rating your services pages, whereas your best keyword “Call Center Services” is not considered.
This would mean re-looking at lots of pages on the websites I am working on, and it’s there in my to-do list now.
All the very best in your online marketing efforts!!