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Forum Moderators: goodroi
If you're a trademark holder on a trademarked term, you can prevent them from using that term in their ad, but you can't block them from bidding on the term.
Are they advertising your product (i.e. not someone else's)? If not, I can understand the concern, but if they ARE advertising your product I don't see why you're unhappy that other people are spending their own money and time trying to sell your stuff.