Keyword Cannibalization and How to Handle It

Keyword cannibalization (no matter how awfully terrifying it may sound) is a widely-spread website internal information structure problem that occurs when multiple subpages are (heavily) targeting one and the same key term.
Very often webmasters are unaware of any keyword cannibalization problems throughout the site - for example, (partial) internal duplicate content issues caused by the site CMS (e.g. pagination causes multiple pages with one and the same title) can account for it.
Others intentionally optimize several pages for one key term “to strengthen” the effect: they think the more a keyword is used throughout the site, the more important it seems for a search engine.
Keyword cannibalization is the issue not to be taken lightly because:

• It causes inadequate index and crawl depth by forcing Google to choose between many pages and pick one it feels best fits the query “filtering” the rest of relevant pages;
• It accounts for lower SEO effectiveness: efforts are not focused: you are spreading link power, keyword targeting, and anchor text on your site across multiple pages.
• It causes internal site competition: your own pages compete with each other for a position in Google.

How to avoid or solve keyword cannibalization problems?

• Get rid of internal duplicate content issues;
• Organize your keyword lists to thoroughly think through the internal information structure:

Here is also a useful discussion on optimizing your site for multiple keywords.

• Carefully think over your website architecture to make the most of internal anchor text and keyword prominence.