My thoughts exactly. Bing isn't the go to search engine for a majority of people so the primary areas I can see it being used is on mobile devices where the option to open a new google search tab isn't as simple as on your desktop.

Actually my first thought when I read the article was "25% of nothing is still nothing" ;) but maybe that was a bit harsh. Bing is after all being used by people who simply can't be bothered to change the default search engine.