Citigroup (NYSE: C) recently revived advertising slogan is reassuring: "Citi never sleeps." The idea is that since it operates in 100 countries, there is always a Citi employee on the job. But even if you have 300,000 employees, a company can only survive if those people are doing the right things when they're on the job. If not, Citi might never sleep, but it could take a dirt nap.

Citi stock has lost half its value this week and, at $4.71, is down 92% from its September 2000 high of $57.50. Prince Alwaleed said it was dramatically undervalued -- and that was yesterday morning before it lost 26% of its value. I suggested yesterday that the Prince may have miscalculated. How so? If you think that value can be measured by comparing the stock price to potential earnings growth, then I think the Prince overestimated the earnings growth part . For instance, its global cards and consumer lending business makes up 67.3% of net revenues, and global cards shrank 40% in the third quarter.

Since the prince has so much of his diminishing wealth -- his investment fund was down 63% as of yesterday -- tied up in Citi stock, he may have decided that people's memory of his 1991 investment killing based on buying at split-adjusted $2.98 -- will draw in buyers. But things are different now. Citi has posted huge write-downs in four consecutive quarters of losses totaling $20 billion; nine of its investment funds have collapsed this year; it will lose money due to write-offs of consumer loans, commercial real estate, and mortgages; and it has trillions of exposure to derivatives and illiquid assets.

In a move that was long rumored, Citigroup Inc. (NYSE: C) is getting a $7.5 billion cash infusion from the investment arm of the government of Abu Dhabi, according to the Wall Street Journal. (subscription required)

"The investment by the Abu Dhabi Investment Authority will help rebuild Citigroup's capital levels, which have been eroded by a credit crunch that began in August. Citigroup Chief Executive Officer and Chairman Charles Prince resigned earlier this month after the bank, which had already written off billions of dollars, was facing as much as $11 billion more in losses," the paper said.

ADIA will become one of Citigroup's largest shareholders with a stake greater than Saudi Prince Alwaleed bin Talal, reportedly the company's largest individual shareholder, people familiar with the matter told The Journal.

News of the investment should give a boost to Citigroup's shares which have tanked about 45% this year and perhaps other financial stocks including Merrill Lynch & Co. (NYSE: MER) and Bear Stearns Cos. (NYSE: BSC), which are down as much as Citigroup

That impact, though, may be short-lived because there may be another shoe or two still left to drop in continuing saga of the subprime mortgage meltdown.

Those of you reading this while jammed into a center coach seat might want to move on to another story, one that doesn't deal with a Saudi prince's new ride, the 6,000 square foot 'Flying Palace" custom Airbus A380.

Billionaire Prince Alwaleed bin Talal is paying well over list ($320 million) for his sky limo/air estate. While Airbus would not reveal details of the customization, the possibilities are vast. The cabin is as wide as three Shaquile O'Neils laid end to end, as long as six Weinermobiles, with as much area as 24 rooms at Motel 6. That's plenty of room to pimp it up with a swimming pool, or a go-cart track, bowling alley, IMAX theater, quilt loom, foosball, lawn darts or Frisbee golf course, or sauna complete with its own live birch trees. Think on that the next time you try to prop your laptop on a tray the size of a dollar bill.

This is not the Prince's initial foray into luxury air travel. He is presently the only owner of a private Boeing (NYSE:BA)747, which will probably become his beater plane, the one the kids take to college.

I can picture Sandy Weill, the former chairman of Citigroup (NYSE: C), now. He's probably pacing the floor of his penthouse apartment, wringing his hands, sweating, perhaps yelling into the phone at someone when he gets a chance. He must be all in a lather about Citigroup's drop in share price (down another 5% so far today to $35.91).

I co-wrote a book about Sandy Weill that came out in 2002 and one thing Mike Brewster and I posited is that Weill would like to run Citigroup until he met his maker. That wasn't in the cards, since he had to step down in 2003 after a series of scandals rocked the bank. And calling Weill the King of Capital, as we did in our book (King of Capital: Sandy Weill and the Making of Citigroup), didn't look so smart not too long after publication either.

Now I've been watching Maria Bartiromo on CNBC reporting that Weill does not want to run Citigroup, but will be happy to help out in the search for a new chief executive. Here's my interpretation: Of course he'd love to jump in and run the company again. He just knows the board could never give him the chance.