if you choose the Customized location targeting option you now MUST enter a zip code. I used to only enter a city and state. I recently changed the city in one of my campaigns (left the state as it was) and did not enter a zip code. As a result, I had zero impressions for that campaign over a 7 day period. When I called Adwords customer service they could find nothing wrong with my campaign settings and had no explanation. When I checked the settings myself, I found that my location was set to approx 250 miles off the coast of Oregon. So watch out!
