The venture capital firm Kleiner Perkins Caufield & Byers set up a $100M fund for iPhone related starts ups. The number of applications has exceeded their wildest expectations, according to BusinessWeek on Wednesday.

In fact, a wager was formed over how many applications they would receive, wrote Olga Kharif. "The wager was over how many business plans they’d receive in the first 30 days after the Mar. 6 announcement. Kleiner Perkins partner Matt Murphy won’t divulge the number, but says it was exceeded within 36 hours."

The interest in iPhone development has been so great that, already, more than 100,000 developers have signed up to write applications.

While many developers are just digging in and see an immediate opportunity, a few are taking a cautious approach, thanks to the wording of the SDK’s NDA or some of the technical restrictions that get in the way of their pre-announcement plans.

Meanwhile KPCB perceives the iPhone as not just another cell phone. "A lot of the pillars, foundational applications for the mobile Internet, will grow up on the iPhone," said KPCB partner Matt Murphy. He thinks the fund could swell to more than US$100M.

While some developers are given pause by Apple’s licensing terms, others are thinking big. Zumobi believes in mobile advertising. Another is Jajah which envisions a Wi-Fi based phone that would sidestep international roaming charges. "If things like this are available, companies will give employees a choice of an iPhone vs. the BlackBerry," said Frederik Hermann, Jajah’s director of global marketing.

In the end, that may be the key. Unexpected, innovative killer applications are just around the corner for those with a vision. KPCB is eager to make it happen.