Politicians do the same thing. I read an article once about how Dick Chaney would identify groups of voters who weren't in favor a Bush administration policy or action (the war in Iraq is an obvious example) and would then identify a issue the majority of that group more passionately supported. (Abortion and gay marriage were two of the more notable ones.) This way, blocs of voters who normally wouldn't vote for Bush would feel compelled rethink their decision.

Now instead of voters, what Google is doing is courting customers. Consumers who may feel passionate about buying locally may be persuaded to buy something online if the targeted ad makes a compelling argument for product's environmental or social policies.