Citi not only took a page from Enron, but is also taking a page from current uber-failures such as Bear and Lehmans. Part of that page reads "reiterate your 'strength' in the face of a crushed stock price and serial capital raising". At the same time as Citi was firing fifty thousand (yep) people on Monday, they were madly spinning that they had enough money and "strength" to make 2009 even better than 2008 lolz!
Anyway. Their stock is down around $3. Which doesn't strictly "matter", in that the stock price doesn't really effect day-to-day operations, except that it does. And it matters because stock price is widely seen, correctly or not, as a measure of health of the company. As the stock slides, some entities (such as pension funds) will have to sell because they have by laws prohibiting them from investing in speculative penny stocks. Other companies will demand more collateral in order to make deals with Citi, which will further erode their capital. And at the root of all that capital are plain old bank deposits, which are provided by the hoi polloi like you and me. Folks are very familiar with getting screwed by having too much dough in one bank (see: IndyMac), so you can expect withdrawals to start happening. And that will be the final crushing which will lead the FDIC to take over the joint.
But why would people start withdrawing? Because the faith runs out.
I had to look up what articles of faith actually are - a list of beliefs professed by some Christian sect. "We believe in the Bible is the word of God". Essentially a first principles document for your sect.
But it all starts with that "we believe". That belief underlies not only the revealed wisdom of Christianity but also that of capitalism. For even the most basic of economic transactions, there has to be a level of trust and belief (i.e., this horse you're trading me isn't sick or full of greeks). As you move past barter into money economies, the trust has to be ramped up. Being able to accept that money is a "store house of value" means that you accept that someone else will accept this. And as you move from asset backed currency (such as the gold standard) to fiat money (such as the money in your wallet right now), trust is the only thing providing value at all.
A bank run is similar. Banks only have on hand a fraction of the money "on deposit" with them. If everyone goes at once, the bank dries up and blows away. Amazingly, if everyone would just calm down, and not try to withdraw at once, your bank would usually survive. But no one wants to be the last one holding the bag, so the rush is on.
(BTW, fractional reserve banking isn't evil at all. It's perfectly normal. If I borrow $100 from you and then let another friend of mine borrow $50, I have just engaged in fractional reserve banking. Though I still owe your $100 - or, to look at it another way, you have $100 of deposits with me - I now only have $50 on hand.)
The same thing would happen if your mortgage company all of a sudden demanded the rest of your mortgage get paid off this month. It's likely you wouldn't be able to, and would have to declare bankruptcy.
So trust underlies the banking system, and indeed the whole financial system.
But what else does it underlay? Personal relationships, naturally. Work relations, too. Sometimes you can tell that folks have lost the confidence of their peers and that they're sliding out. Or the company itself has lost confidence in its business plan and it's falling apart.
I think it's relevant that parliamentary governments hold "votes of no confidence" in order to drive someone out.