An upcoming cover story in FORTUNE magazine reveals internal disarray at Google, and raises troubling questions about the company’s future. The story comes out as talk continues to swirl about Google’s expected IPO next spring, which could raise as much as $2 billion. The story, “Can Google Grow Up?” appears in the December 8 issue of FORTUNE, available on newsstands December 1 and at www.fortune.com on November 24.

FORTUNE talked to Google founders Sergey Brin and Larry Page, CEO Eric Schmidt, and top executive Omid Kordistani. In addition, FORTUNE conducted more than two dozen interviews with employees, investors, business partners, and people exploring employment or business deals with Google, along with veterans of the search, online advertising, and computer business – and what it found was a talented company facing trouble.

“(Google) has grown so fast that employees and business partners are often confused about who does what,” reports FORTUNE writer Fred Vogelstein. Stock- and option-stoked greed is creating rifts within the company, and heated questions continue about who is really in charge: CEO Eric Schmidt or co-founders Brin and Page, reports Vogelstein.

As one CEO puts it, “My take is that they are crumbling under the weight of their own success.” Says an investor, “Google has a lot of momentum, but its current position is probably not defensible.”

The bottom line? Google’s numbers are strong and revenues continue to soar. But with competitors gearing up for a search-engine battle and turmoil within, Google could be worth much less by the time investors in the IPO are able to cash out.