A WebmasterWorld thread spots Google in violation of their own AdWords policies.
Google clearly has a policy that says:
Google does not permit multiple ads from the same or affiliated company or person to appear on the same results page. We believe that pages with multiple ads from the same company provide less relevant results and a lower quality experience for our users. Over time, multiple ads from the same source also reduce advertiser performance and lower their return on investment.
The thread pointed out that a search for maps brought up two ads from Google. One for earth.google.com and maps.google.com. Honestly, both are different products, so I am not sure why AdWordsAdvisor said "it was a case of human error - now corrected."
But I guess this is not allowed and that Google violated their own guidelines.
Forum discussion at WebmasterWorld.
