Wells Fargo & Co. (WFC) routinely ducks hard questions from investors. That insistence on silence has lately hurt the San Francisco bank's stock.

Wells Fargo is surely one of the strongest survivors of the financial crisis thus far, having gobbled up crumbling rival Wachovia Corp. at a fire-sale price last year. That merger made the one-time West Coast bank a national powerhouse of retail banking, with more than 10,000 branches and $1.3 trillion in assets.

But Wells Fargo's stature didn't prevent its shares from falling abruptly Tuesday amid a swirl of unfounded rumors. The shares fell as much as 6% during the day before recovering after CEO John Stumpf's said the bank doesn't plan to raise more capital to pay back government bailout money, which can hurt existing investors.

The stock's wild ride in part reflects investors' growing unease over Wells Fargo's refusal to mimic the routine disclosure practices of its large-bank rivals. Whereas JPMorgan Chase & Co. (JPM), for example, provides extra detail about the condition of its operations, Wells Fargo says as little as possible.

"They don't go out of their way to keep the investment community fully informed," said Frank Barkocy, director of research at Mendon Capital Advisors Corp. "I think that tends to lead to some volatility in the stock."

A spokeswoman for Wells Fargo declined to comment for this report.

Shares in Wells Fargo recently traded up 0.5% to $26.34. The stock is down about 11% year to date; that fall is less than the 32% decline at Citigroup Inc. (C), but well behind the rise of 17% at Bank of America Inc. (BAC) and the 31% rise in JPMorgan shares.

Wells Fargo is the only large bank that refuses to hold a quarterly conference call to discuss its earnings - a prime opportunity for investors to ask questions of company executives. The bank also won't disclose its tangible book value per share, a statistic that became a focus of investors during the financial crisis, and that other banks routinely provide.

Perhaps most importantly, Wells Fargo has repeatedly refused to say exactly how the troubled loans it purchased with Wachovia are faring. Even ardent supporters have taken note.

"I like the company, but...they really need to step up their disclosure and transparency," says Nancy Bush, founder of NAB Research LLC. "The shares bear the brunt of that."

The company could now be feeling some more pressure to talk.

The number of investors betting that Wells Fargo's shares will fall has grown in recent weeks. Meanwhile, the bank has recently hired a new head of corporate communications.

To be sure, the bank's management and outlook remain well regarded among industry observers. In fact, one large-bank CEO told Dow Jones Newswires last week that Wells Fargo has one of the strongest brand names of any company in the world.

But the lack of information from the bank's management has led to a growing debate over the bank's outlook - and especially how its shares will perform the rest of the year.

Said Stuart Plesser, an analyst at Standard and Poor's: "It's probably the most interesting story in the banking space."

-By Marshall Eckblad, Dow Jones Newswires; 212-416-2156; marshall.eckblad@dowjones.com