So far the U.S. has committed $12.8 trillion to bailing out Wall Street. Does this mean that Wall Street CEOs made mistakes? Apparently not. Because if it did, the Wall Streeters who cost taxpayers all that loot would be out of their jobs.

A few have moved on -- consider Merrill Lynch's former CEO Stan O'Neal, who, after leaving the investment bank with a then-record $2.24 billion loss, received a "kick in the rear" amounting to a $161 million retirement package. (O'Neal is just one of the Harvard MBAs whose destruction of the global economy is prompting some navel gazing at HBS.)

Most, though, are still at their desks, gamely calling the shots. Yesterday, Treasury Secretary Tim Geithner suggested it could be time for that to change.

Harvard's business school (HBS) has been celebrating its 100th anniversary this year. And it looks to be at the peak of its power. That's unfortunate because five of its most powerful graduates have made significant contributions to absolutely wrecking the global economy. HBS admits people who are natural leaders. Unfortunately, many of the most powerful of these leaders have followed the path of destruction.

Here are five Harvard MBAs who wrecked the economy:

• George W. Bush ('75). The best thing I can say about Bush is that he said he was sorry for all the problems that occurred while he was in the White House. Unfortunately, he seems to believe he was a victim of events outside his control. One of his HBS professors said of Bush "He showed pathological lying habits and was in denial when challenged on his prejudices and biases. He would even deny saying something he just said 30 seconds ago."
• Hank Paulson ('70). As Treasury Secretary Paulson has consistently ignored the severity of the financial crisis -- In June 2006 he gave a speech at HBS in which he said, "this is by far the best global economy that I have seen in my career" -- but this September he was able to sell Congress on an ineffective plan to fix what he finally realized was an imploding economy -- a plan has kept changing. The economy has continued to crash despite his bone-headed efforts to save it.

Merrill Lynch & Co. (NYSE: MER) is planning to cut year-end bonuses in half in a show of fiscal discipline.

Why stop there?

Shares of the New York-based company are down more than 78% this year. Keep in mind that Bank of America Corp. (NYSE: BAC) agreed to buy the once-venerable firm for $50 billion, a deal which is still making its way through the regulatory process. Did I mention that Merrill and Bank of America got a combined $25 billion from the Treasury Department and that Merrill may lose $13.3 billion this year, based on the average estimate of nine analysts surveyed by Bloomberg? That's more than double from a year earlier.

What in that sorry performance merits a reward of any sort? Wall Street needs to ween itself from the notion that everyone deserves a bonus, regardless of the macroeconomic environment. Top executives at Goldman Sachs Group Inc. (NYSE: GS) and UBS AG (NYSE: UBS) are refusing bonuses. Heck, so are the heads of the tone-deaf auto industry.

Merrill has already been very generous with its employees. Chief Executive John Thain got a $15 million sign-on bonus when he joined the company with the expectations that he would fix the mess created by Stan O'Neal. Given the turn of events, maybe he should give some of that money back. In 2007, the company paid out $15.9 billion, about $248,000 per employee.

Lehman Brothers Holdings Inc. (NYSE: LEH) Chief Executive Richard Fuld, Wall Street's longest serving CEO, has no reason to fear being ousted if he can't turn around the company around. In fact, on some level, he may welcome it because he stands to reap more than $241 million.

Fuld, who has been Lehman's chief executive since 1993, and other members of Lehman's senior management team do not have employment contracts or change in control bonus arrangements, according to the company's most recent proxy statement. He is also declining a bonus for this year for obvious reasons. Nonetheless, his turnaround effort announced this morning, which includes slashing Lehman's dividend by 93%, selling a 55% stake in its investment management division and a spin-off the vast majority of its commercial real estate assets into a public company, got a mixed reception on Wall Street.

Shares of the New York-based company, which fell 45% yesterday, tumbled in pre-market trading. They later rebounded following Lehman's conference call which Fuld personally oversaw. But as my colleague Peter Cohan noted, the company's earnings, which were issued a week early, were even more awful than Wall Street expected. The company reported a preliminary net loss of $3.9 billion, or $5.92 a share. Net revenue was a negative $2.9 billion.

Democratic presidential candidate Barack Obama today sharply criticized the pay packages given to the departing chief executives of Fannie Mae (NYSE: FNM) and Freddie Mac (NYSE: FRE).

Obama told reporters that he wrote letters to Treasury Secretary Henry Paulson and Federal Housing Finance Agency Director James Lockhart stating that "it would be unacceptable for executives of these institutions to earn a windfall at a time when U.S. Treasury has taken unprecedented steps to rescue these companies with taxpayer resources," according to CNBC.

He's absolutely right.

Yes, I realize that compared with the fallen CEOs of Wall Street, the pay packages are chump change. Fannie Chief Executive Daniel Mudd is 'only' getting around $9.3 million and his counterpart at Freddie Mac Richard Syron stands to receive $14.1 million. But just because Mudd and Syron are getting less than 10% of the $160 million parting gift awarded to Stan O'Neal for ruining Merrill Lynch & Co. (NYSE: MER) does not make them any less egregious.

Pity the hapless ex-CEO who has to explain to the U.S. Congress how he got millions for failing at his job. It's like the person in the horror movie who doesn't realize that a bad guy is lurking in the dark woods even though that's clearly indicated by the scary music. In this case, the knife-wielding psycho Jason Voorhees is being played by Rep. Henry "I haven't met a microphone I didn't like" Waxman (D-CA).

What did former Countywide Financial Corp. (NYSE: CFC) Chief Executive Angelo Mozilo, former Citigroup Inc. (NYSE: C) CEO Charles Prince and former Merrill Lynch & Co. (NYSE: MER) head Stan O'Neal expect to happen? That they would finally be able to tell their "side" of the story? That they would be able to counteract media perceptions that they are a bunch of greedy pigs who were rewarded for their incompetence? Apparently, these once mighty kings of the boardroom were that deluded.

Mozilo was the most outrageous, telling the House Committee on Oversight and Government Reform that, "In short, as our company did well, I did well." The Wall Street Journal (subscription required) noted that Waxman, who locked horns recently with baseball great Roger Clemens, wasn't buying it.