I agree this is odd. Especially seeing as Safari uses google to search. I've looked all over my preferences trying to change it to google with no luck.
Do you mean that your initial web searches, not Spotlight searches, are being directed to Bing? If so, go to Safari preferences and check the search tab to make sure it is set to Google (or whatever else you prefer).
What extensions do you have installed in Safari? One of them may be overriding the settings.