Mobile was once an afterthought in the advertising world — but today, brands are perking up and paying attention, as mobile is growing faster than all other digital advertising formats in the US. With new smartphone releases, most clients are developing a mobile strategy. And while advertisers agree the platform has a ways to go before they can develop a viable advertising strategy, more and more marketers want in on the mobile game.The dilemma is that traditional methods of advertising often don't translate well on mobile — and there's far less screen space on mobile than desktop. It's clear that brands and advertisers will need to get creative in order to develop successful mobile strategies.But BI Intelligence expects that this gap will narrow substantially, as enthusiasm grows for mobile-optimized ad formats (such as interactive rich media and native ads), as targeting improves, and more and more advertisers learn how to effectively use the platform.In-app mobile ads perform much better than mobile web ads, and ad spend will likely follow performance and usage. In-app click-through rates averaged 0.56% globally compared to 0.23% for mobile web ads during the first half of the year, according to Medialets.Ads on apps get much higher click-throughs than ads on the mobile Web: 0.58% on apps vs. only 0.23% on the mobile Web.It’s worth noting that travel and entertainment ads do especially well, getting about a 60% higher click-through rate than ads for retail, automotive, and other categories. That’s probably no surprise, given that people are using smartphones on the go.