The Google AdWords team has posted their official stance on trademark usage in paid search advertising in two parts:
Part One
Part Two
It’s clear that Google believes that in the United States, usage of trademark terms in keywords is acceptable, but usage of trademark terms in the advertising copy is not.

Official Google Webmaster Central Blog:
They make it fairly clear that the result of duplicate content is filtering, not penalization.
They also chime in with some info on international sites:
“Though we do offer a handy translation utility, our algorithms won’t view the same article written in English and Spanish as duplicate content.”
“Use TLDs: To help us serve [...]

Marketing Pilgrim:
Clever title and great analysis.
Yes, he takes a distinctly negative slant, but raises good points.

E-Commerce Times:
Baidu will be providing ads for Microsoft’s Chinese sites this month. It is quite possible that Baidu represents the most legitimate threat to Google’s supremacy in the search engine wars.

WebTrends Acquires ClickShift

Inside AdWords:
The Google AdWords team has released more on their landing page scoring system.
Unfortunately, they don’t give much in the way of interesting info here. The only real point they make is that the scoring system used for content advertising is different than the one used for search advertising.