Mobile gaming is growing rapidly, so it’s no surprise that marketing dollars are following the money. A new study found 70 percent of marketers plan to increase budgets for mobile in 2013. Mobile ad spending in the U.S. is expected to reach $2.6 billion this year, including spending on display, search and messaging-based formats. Mobile advertising on smartphones is projected to be a $5.04 billion industry by 2015.

“A lot of brands have spent far too much money on mobile applications,” said Scott Forshay, a mobile and emerging technology strategist for emarketing company Acquity Group. He’s not a fan of that spending, though., saying, “Of that $2.6 billion spent, $2.5 [billion] of that was probably wasted.”

The reason it’s wasted Marketers are just taking what they do on other platforms and shrinking it down for smartphones, ignoring the differences in how people use their smartphones.

“Probably the biggest error brands have made as they venture into mobile is that they think mobile is the same thing they’re doing for the website, just down to a 4-inch form,” he said. Marketing on mobile devices will need to be timely, personal and contextually relevant (people expect their phone to be customized to who they are), in order to work.

Brands that understand who is shopping and what problems they can address for the consumer are successful, Forshay added. He suggests brands take a step back to find out who their consumers are, if they’re using smartphones, and if the majority are using iOS or Android.

He also didn’t see much value in banner ads on things like Zynga games and some apps, citing the “fat finger principal.” In some studies, he says, it’s been shown that up to 76 percent of clicks on mobile banner ads are caused by an accidental touch.

Read more about Forshay’s thoughts at Mashable.com.