Spotted via Steve Rubel, Apple Cracks Down on Google AdWords at TidBITS suggests that Apple may be pushing on Google to enforce rules preventing advertisers from having ads show up in response to its trademarks in Europe.
Though the ads were initially said to have been stopped because of the use of the word "Mac" in the ad text, it later turned out that the complaint involved ads targeting that word that were showing up in the EU. The solution seemed to be restricting the ads to show up only in the US.
Google's trademark policy differs in the US and the UK. In the US, you can target ads to show up in response to terms that are also trademarks. You simply cannot use trademarked terms in ad COPY, if a trademark holder objects. In the EU, Google may restrict the ability to target ads to show up in response to terms that are also trademarks AND/OR the use of those terms in ad copy.
Why? Google has faced different lawsuits. In the US, the GEICO case found that linking ads to terms that are also trademarks was not confusing nor a trademark violation. But the court did think the use of trademarked terms in ad copy potentially might be confusing. Google's policy in the US gave it an end run around this.
In the EU, Google's lost cases about ads being triggered by terms that are also trademarks, thus the tighter policy.