Search is different. Searchers use the same medium--the engines--to do their initial research, as they do to learn about later buy-cycle information. They'll search to learn what kinds of cars are safe and which get good MPG; they'll also search, later on, to find a dealership that's nearby. Traditional media silo the buy-flow; search unifies it.
The fact that search unifies the buy-flow means a lot for search branding. That's because, as a searcher searches more, she isn't just gathering more information--she's placing a deepening trust in the engines as an information source. So displaying your ad at every point on the buy-flow creates a double win: you get your name out; and you leverage the faith that searchers place in the engines themselves.
The two parts of branding
I'll put it a little more precisely. Branding accomplishes two different things: It familiarizes people with you and gets them to like you; it also makes them feel that you're relevant for their particular need. Traditional branding is great at making people like you, but it's less capable at conveying the idea of relevance.
Getting people to like you, after all, is largely an issue of familiarity. And simply because they're everywhere--from your bus stop to your living room--traditional ads are great at generating familiarity. But being relevant means you've near-perfectly matched a consumer's checkoff list, which is something that's a lot harder to communicate through repetition alone. Often, people want a third party to verify relevance.
And since people don't see televisions, or magazine glossies, or even brochures as a source of relevant product or service information, the mere presence of your ad in those media won't increase your stature as a relevant brand. Search, on the other hand, is built entirely on relevance--and so being present in the engines carries the associations of the engines' relevance with it.
Search branding is good branding
That distinction can mean a lot as a searcher goes through the buy-flow--a process that, typically, includes between three and five unique searches. Over the course of those three to five searches, consumers go from uninformed shoppers to educated buyers; and while an uninformed shopper makes decisions primarily based on who they like most, relevance becomes a much stronger factor for the educated buyer--who might be looking at buying more rationally, because she's out to find specific product features, types of service, and value levels. And, in marketing, the endgame isn't appealing to shoppers at the beginning of the buy-cycle. The endgame is to make yourself appealing to shoppers at the end of the buy-cycle, when they're going to make a purchase.
Which is why it's as important to create branding that conveys relevance as it is to create branding that generates familiarity. And it's why advertising through search from the start of the buy-cycle can be so powerful for achieving conversions at the buy-cycle's end. The more searchers see you in the engines, the more they'll associate you with the overall relevance the engines provide--and that association can really pay off when they're figuring out where to buy.
(This all assumes, of course, that you've got the ability to parse keywords according to buy-cycle stage; that you can create ad copy that's tailored to phases in the buy-cycle; and that you have the analytics to create cost-efficient branding campaign--but that's a topic for another piece.)