As far as Google PPC goes, if your trademarked term shows up on a competitors “ad text,” they will notify the other company of the issue if you bring it to their attention. (You have to prove to them that it’s trademarked though….which you also have to do if you want to put the trademark symbol in your ad.) However, Google won’t step in if the keyword is just in their keyword list and they are bidding on it. If a company feels strong enough to go after them anyways, the best thing to do is send them a cease and desist. That will take care of about 90% of those issues.

But based on my experience and ethics, I don’t support companies that bid on competitor keywords. Its a short lived bottom feeding strategy in most cases. However, in certain cases such as a travel aggregator like “Expedia” bidding on “hilton hotel” kewords, I feel that its more acceptable. Anyways, that’s my two cents!