Trademarking your key words

I can't think of a good way to accomodate the trademark owners' legitimate interests, without essentially shutting down word-based ad placement services. And in the absence of such a solution, it seems to me better to let the ad placements go on.Freedom to Tinker: Trademarks and Ad Placement

Good overview of American Blinds vs. Google, who essentially say they own the copyright to the keywords "american" and "blinds" when used together, thus making it infringement if Google displays competitive ads next to that keyword phrase.