It’s been two years since Apple (NSDQ: AAPL) first started selling applications for the iPhone through the App store. In that time, investors have flocked to the opportunity, pumping slightly more than $100 million into 17 companies.

The figures are being reported today by “the ChubbyBrain database,” which keeps a running tally of venture capital investments in the U.S. So, is that a lot? That question was too difficult for ChubbyBrain to wrap their minds around, but likely the answer is that the pace is falling somewhere between exorbitant and on par with the opportunity.

Given that the U.S. is facing what has been called the worst downturn since the depression and that the iPhone and App Store are completely unproven, the bets are definitely risky. But at the same time the iPhone ecosystem is receiving a lot of hype. The market has been flooded with more than 50,000 apps and more than 1 billion have been downloaded.  The two biggest proponents are the Kleiner Perkins Caufield & Byers’ $100 million iFund aimed at iPhone application developers, and RIM’s $150 million Blackberry Partners Fund created with Canadian firm JLA Ventures and the Royal Bank of Canada. Given that kind of attention—and dollars—it can be interpreted that investors are actually showing some constraint.

Breakdown of companies by industry: The top three areas of application investing falls into the categories of Social Networks (31 percent); Gaming and Entertainment (22 percent); and tied in third is SMS (13 percent) and diversified application development (13 percent).

Breakdown of money invested by industry: The top three areas of application investing by dollar amounts are Social Networks (27 percent); Gaming and Entertainment (22 percent); and Monitoring and Security (20 percent).

Average funding: The average level of funding was $4.7 million, the median was $3.5 million. The largest deal garnered $15.5 million, and the smallest deal received only $15,000. The most active VC was the iFund with six companies (in eight rounds) totaling $50 million.

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