If you're still wondering if it's the year of mobile, you've already missed it. While the medium pales in advertising dollars spent -- just $6.4 billion worldwide in 2012 -- it occupies an outsized place in the marketer's consciousness. Why? The smartphone, now carried by nearly half of all Americans who own a mobile phone, is a computer, a camera, a map, a compass and, for a small-but-growing number, a wallet.

Mobile e-commerce

While widespread use of the mobile phone to pay for things seems a way off, the phone is now dictating buying decisions as much as any devices before it. Consumers are using phones to comparison shop in stores; they are using them to consult reviews on products, services, hotels and restaurants; they are using phones to tell their friends where they are and what they'd like to do. Oh, and they also buy things. Even more than the PC, the phone is a transaction device, so it should surprise no one that search advertisers dominate in mobile.

While Apple, Google, Jumptap and others would like to turn the phone into a branding medium, search spending is expected to outpace display for at least the next several years, according to eMarketer. Global spending on banners and rich media is expected to reach $1.5 billion in 2013, while search goes up to $2.2 billion.

Two-platform world

While smartphones boom, two platforms are becoming dominant: Google's Android and Apple's iOS. Meanwhile, the once-huge BlackBerry is declining precipitously from more than 23% market share in June of last year to about 10% today with nothing in the pipeline that promises to slow down its decline. Microsoft's Windows Phone has latched itself to ailing handset maker Nokia in hopes of breaking in, but it's a longshot and Hewlett-Packard's Palm could disappear soon as well. Among handset manufacturers, Samsung has ridden Google's Android to a dominant position in the marketplace, forcing Apple to accept a smaller, niche role.

In the past year, Google closed on its $12.5 billion deal to buy Motorola, a once-mighty trendsetter in handsets that didn't see Apple or Android coming. What Google does with Motorola could shuffle the landscape once again.

Award-winning work

It shouldn't surprise anyone that Google has become an adept mobile marketer in its own right, winning the first mobile Grand Prix award in Cannes this year. What won? Google used mobile technology to re-imagine one of the most iconic TV campaigns of all time, Coca-Cola's 40-year-old "Hilltop" ad.

View Ad Age 's Mobile Marketing Fact Pack.