Neither boom nor hedgehog

I've been wondering about the following for some time now, but forotten to blog about it: While in New York City, I've been seeing commercials for the fast-food restaurant "Sonic." Having checked Sonic's web-site to confirm my gut instinct, I notice that there are no Sonic locations in the tri-state area of New York, New Jersey, or Connecticut. In this instance I saw it on a cable channel (USA, to be precise) but I believe I've seen the ads on networks in the past. I won't swear to that last part though. The answer to the question I'm about to ask could then just be that USA sells some of its ads natioanlly, but I really think I've seen them on networks. So the questions are: Can you think of other non-national companies that advertise natioanlly? Why would they do this? Is it possible that the sum of costs the ad-buys for all the individual areas Sonic needs to target would be greater than a national ad-buy?