WASHINGTON - After countless new rules designed to make Wall Street safer, it's come to this: Another securities firm has collapsed from risky, poorly disclosed bets.

Not enough, in other words, has changed since the U.S. financial system nearly toppled three years ago.

The bankruptcy filing last week by MF Global Holdings Ltd. didn't freeze lending and panic investors around the world, as Lehman Brothers' did in 2008. But the rapid fall of the firm run by former New Jersey Gov. Jon Corzine shows risky behavior persists, despite a vast regulatory overhaul.

As lenders abandon Italy this week and stocks plummet on fear that defaults in Europe are all but inevitable, those new rules are about to be put to the test. One question no one can answer: Is the financial system, with its expanding web of connections that even experts can't trace, any safer?

"People are making the same dumb bets," says investor Michael Lewitt of Harch Capital, who calls Washington's new rules inadequate.

MF Global's collapse suggests that:

* Financial companies are making risky bets with borrowed money and hiding them off their balance sheets. In MF Global's case, scant disclosure made it harder for people to see the danger until it was too late.

* Those bets are being made with their own money, but threatening customers and trading partners. Dodd-Frank, the Wall Street overhaul passed last year, focused on big, complex financial companies whose failure could topple other firms. The law bans these "systemically important" companies from making such bets with their own money, called proprietary trading. But it does little about smaller financial firms like MF Global.

* Many financial companies operate without coordinated oversight by regulators. MF Global was watched over by several regulators. But no one was in charge of coordinating them. Financial companies, aside from the biggest, face the same patchwork oversight that failed to stop risky bets before the financial crisis.

The bust of MF Global itself is not an indictment of the new rules. Dodd-Frank wasn't designed to prevent all financial failures. In fact, some failures can be healthy if they discourage investors from taking on excessive risk.

But MF Global's collapse brought heavy costs. It caused millions in losses for investors. It threw commodity markets into disarray. And it left customers confused and angry because $593 million of their money is missing.

"The question for regulators is, 'How did this happen?"' says David Kotok, a money manager at Cumberland Advisors. "Could we have seen it coming?"

The answer: Yes - but you had to look hard.

MF Global failed after buying billions of European government bonds on a hunch they were less risky than many investors assumed. The trouble wasn't so much the bet itself. It was how the firm disclosed it and financed it.

MF Global didn't recognize those bonds on its balance sheet for all to see. Instead, they were shunted "off-balance sheet," their presence noted deep in its financial statements. Some separate filings with regulators excluded them entirely.

This sleight-of-hand was possible thanks to an accounting maneuver used by Lehman to hide its debt before it failed: Instead of holding onto the bonds it had just bought, MF Global "sold" them to other companies in exchange for cash - with the promise to buy them back later.

In effect, it was borrowing the cash but not calling it that since technically it came from a "sale." And because the bonds were off its books, MF Global didn't have to acknowledge the risk they posed.

Other firms have struck similar off-balance-sheet deals, but poor disclosure makes them difficult to track.

The lack of detail about financial companies' holdings can lead to panic selling. Fearing another MF Global, investors started dumping shares of broker Jefferies Group Inc. last month. The stock recovered after the company released details showing its bets were smaller and not funded by the same off-balance-sheet deals.

Janet Tavakoli, president of Tavakoli Structured Finance in Chicago, says the hidden debt at MF Global makes her wonder if regulators have learned anything from the financial crisis. She notes that American International Group Inc. used off-balance-sheet "swaps" to bet that U.S. homeowners would pay back their mortgages - that is, until it collapsed and had to be bailed out by taxpayers.

"We've seen this movie before," says Tavakoli.

Under Dodd-Frank, large financial companies that played a big role in the financial crisis are subjected to new, stricter oversight. But that's not the case with smaller firms.

Christopher Whalen, managing director at Institutional Risk Analytics, notes that banks must file quarterly "call reports" listing a wide range of details about their risks - but no such disclosure is required of smaller financial firms like MF Global.

"The problem is, they are still very opaque," Whalen says.

In the case of MF Global, it not only made "proprietary" bets banned at larger firms, it did so with gobs of borrowed money. One measure of that, its so-called leverage ratio, hit 31-to-1 in September, similar to Lehman's before it failed. Most big banks are closer to 10-to-1 now.

Of course, the risks taken by MF Global may prove more an exception than a rule. But Louise Purtle, an analyst at research firm CreditSights, is worried. She wrote in a report last week that, as regulators crack down on the largest financial companies, risk could be building in the "shadow banking system" - the thousands of hedge funds, small brokers, money managers and other non-bank financial firms out of the spotlight.

A recent Federal Reserve report estimated the assets of the "shadow banking system" at $16 trillion last year, up from $5 trillion or so in 1995.

The failure of MF Global highlights another problem: The more regulators watching over a company, the less likely it will be watched closely.

The Securities and Exchange Commission had broad oversight over much of the firm's trading but left day-to-day monitoring to exchange operators such as Chicago Board Options Exchange. Bets on the future prices of oil and other commodities, called futures, were watched over by the Commodity Futures Trading Commission (CFTC). But that regulator deferred to the CME Group Inc., which operates exchanges where futures trade. The Federal Reserve allowed MF Global to join an elite group of "primary dealers" helping Washington sell new U.S. Treasury bonds. But instead of checking for itself if the company was taking undue risks, the central bank relied on the SEC and the CFTC.

"Who was in charge?" says Michael Robinson, a former spokesman at the SEC, now at public relations firm Levick Strategic Communications. "Everyone says, 'I thought it was the other guy."'

An industry regulator, the Financial Industry Regulatory Authority, recognized problems at MF Global this summer and forced it to hold more capital against its European bets. It also alerted other regulators to the risk.

But the others do not appear to have responded until later when the company was sliding toward bankruptcy and its cash was drying up. If regulators had acted sooner, many believe, they could have safeguarded customer funds and prevented the money from disappearing.

Now the watchdogs are playing catch-up. Fearing more MF Global-type blowups, federal regulators Thursday announced they would be auditing every U.S. futures trading firm - large and small - to make sure customer funds are safe.

Wagner reported from Washington. Marcy Gordon contributed to this report from Washington.