Competitors of companies with valid trademarks can now place keywords using those marks in their (the competitors) advertisements to become more prominent in Google search results. For instance, a small fast-food restaurant in Minot, North Dakota, that competes with McDonald's can use "McDonald's" in its Google advertising keywords. By doing so, this small fast-food restaurant would show prominently in search results when people search for "McDonald's in Minot North Dakota."
Using a competitor's trademark in website metadata can be infringement, but it is not always so. It depends on whether the alleged infringer is using the competitor's mark to divert customers from the competitor to him or her. I would argue that using a competitor's trademark in any metadata constitutes using the mark in connection with a good or service, because all websites are essentially advertisements. If you use the a competitor's trademark in advertising keywords for search results, as Google now allows, you are more directly using the mark in connection with a service: advertising. You advertise to get customers. By definition, using another's mark in your ads would seek to divert customers from them to you, thus effecting infringement. So, there will almost certainly be litigation over this in the near future.