Comment: The reason for this is simple.

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In reply to comment: Just tried out Smartpage and (see in situ)

The reason for this is simple.

Google tailors search results based on information it's logged about you between cookies, accounts and your IP address. If you eliminate these factors one by one you'll find the results start to diversify with each step. Heaven forbid you use them as your DNS server, they'll have logged every site you've ever visited by IP as opposed to just what you've searched for.