More search queries would result when frustrated searchers aren't finding what they're looking for. Google doesn't say they have gained new users, just more searches.
Not sure how that's necessarily a positive thing, but that's the way it's being presented. I always thought search engines were supposed to help people find sites, and not become a destination in themselves. I didn't realize there were people who just want to go hang out searching for stuff, never leaving the search site.
I still think a large percentage of Google's market share has always been webmasters constantly checking their rankings. With all the changes lately, I'm certain site owners and those who manage sites for them are doing a lot more searching to determine where their sites ended up.