this article speaks to that a bit more: http://www.heraldsun.com.au/accc-wins-appeal-against-google-...
"An ad headlined with "Honda.com.au" that redirected to car trading website CarSales"
I would love to see real user research on this topic. Google showed pretty well there are a lot of people who are confused, to say the least[1].
It seems that the on appeal, the full bench decided that google was actually responsible - given their algorithms were responsible for placing the ad in the context.
This doesn't seem to be quite the same as the ambush marketing you mention. That would be more placing an ad for "dell" when searching for "elegant mobile personal computer".