I've talked a fair bit about the strength of using radio (or any other off-line medium) to drive search for your business's name, or your "brand."
There's another very strong benefit that I haven't mentioned. It's a bit more complex because there's not much you can do about it. It all takes place in Google's mighty brain, and on your own browser…as explained by SEOmoz.
Personalized search is now on by default. This means that every click, branded search, and expression of a "brand preference" or "brand affinity" in Google's results is likely to result in preferential biasing towards that domain in future searches. A "Google" Pontiac message during this Superbowl wouldn't just send users to their site, it would also mean that tens of millions of searchers would now be "personalized" towards that domain.
This means the more I search for your brand, the stronger your brand will show up in my own searches, on my own computer. This doesn't apply to search results across the web because it is a part of "personalized search" which is an individualized component of Google's system. It's the kind of thing that used to feel kind of creepy to us, but now that we're desensitized, and now that they aren't so blatant about it, feels ok.
Humorous sidenote…if you spend a lot of time Googling your competitors by name, you'll likely see their results go up, and your brand decline on your own computer. Frustrating? Yes. Worrisome? No.
SUGGESTION: If you dominate search results for your name, instead of telling people to "click over to acme-heating.com" start telling them to "Google Acme Heating!"
If you have a generic name like "Denver Heating and Air," this isn't likely to work for you because a search for your name will also show all of your competitors as well.
The truth is, most folks will search for your name anyway because it's easier than remembering your exact domain. Even if they do remember your domain, they're just as likely to type it into Google as they are to type it into the address bar. That's why "google" is one of the most searched phrases on Yahoo and vice-versa. Given the choice (or not knowing the alternatives) people will do the easiest thing.
So, tell them in your ads to do the easiest thing!
Here's the old Pontiac commercial they mentioned in the SEOmoz article: