Venture capitalists say mobile is the future and this year they're putting their money where their mouths are. A report from M&A firm Rutberg & Co. covering the first half of 2012 shows firms invested $3.9 billion in mobile companies, everything from Jawbone and Viddy to Vox Mobile and Tango. That total is already 7 percent more than all the mobile-focused investments made in 2011, and 46 percent of all the venture capital invested in tech companies so far this year.

Image: Rutberg & Co. Graphic: Rutberg & Co.

Companies targeting consumers raised the most of any single category, $1 billion in venture capital. That category is made up almost exclusively of app development startups, companies like Highlight, Instagram, and Path. Most of these mobile app companies don't yet have a clear business model, or are making what scant revenue they do have from mobile ads. That hasn't stopped them from raising big rounds with VCs. Path raised $40 million, and Instagram raised $50 million this year right before it was bought for $1 billion by Facebook.

App-development startups may have dominated in overall money raised, but device, payments, and infrastructure companies raised the largest individual rounds, especially those focused on the Chinese and broader Asian markets. The biggest mobile round, $216 million, went to China-based cellphone OEM Xiaomi Tech. Chinese mobile payment company Lianlian Pay banked $125 million in VC. Italian Wi-Fi hotspot and wireless broadband company Linkem raised $90 million.

The biggest surprise for Ranjeev Chand, research analyst for Rutberg & Co and author of the report, in the data has been all the money pouring into early stage and later stage mobile device companies. "When I first came to Silicon Valley 11 years ago, there wasn't a soul who wanted to invest in a device company," Chand says. "Now there's a proliferation of device companies, ranging from mobile health to accessories for smartphones."

But Chand warns that just because young mobile companies are finding it relatively easy at the moment to raise seed-stage cash – amounts ranging from $100,000 to $500,000 – doesn't mean the largesse will continue as they go after funding that can range from $1 million to tens, even hundreds of millions. "It will be a lot harder for them to raise series A, B, or beyond," Chand says. "Most of the companies that raised seed funding won't make it to the next level." What will make the difference? According to Chand, start with engaging your users, then deploy a business model that can convert all those rabid fans of your mobile product or service into steady, predictable revenue - ideally a lot of it. As Facebook has shown everyone, if you can't make mobile pay, you don't have much to sell.