A thread at Search Engine Watch forums named Pathetic Trademark Laws discusses a case where someone was not able to use the word 'target' in ones title of the ad. For example, the advertiser wanted to say "Reach your target audience today".
The issue here, at least the popular thought, is that Target is a popular brand. So Target asked Google to put the word "target" on some sort of blacklist. The advertiser is automatically not allowed to submit the ad with that word in the copy. The advertiser will have to ask Google for an exception.
Has Google gone too far with this? Can you blame Google or the trademark lawyers? Or is this just the game that must be played? A whole new discussion.