You own a company with 100,000 ukp of stock.
Every year you sell 20% of your stock [sales of 20,000 ukp] from which you make 10,000 ukp profit.
If you had 200,000 ukp of stock you estimate that you could sell 40,000 ukp of stock and make 20,000 ukp of profit per year!
Nice.
You go to the bank and they say they will will lend you 100,000 ukp if you give them 5% of the loan per year for the next 25 years [125,000 ukp total].
You say great! I can pay the bank 5,000 ukp per year and still make an extra 5,000 ukp myself ie an extra 125,000 ukp over 25 years!
Not as good as 20,000 ukp but 15,000 ukp is surely better than 10,000 ukp!
Nice - it's a win-win situation called 'trade' and all goes well for several years.
Only a nice man like Senator Obama comes along and says to the banks - unless you give home-loans to people who cannot afford to repay them I will use the law to punish you for being 'discriminatory.'
So banks and other financial institutions say yes-siree and all the money that would have been spent buying your stuff is now being spent in the housing market creating a government induced capital misallocation aka 'a bubble.'
And suddenly you are not selling 20,000 ukp of stock per year - you are not even selling 10,000 ukp per year - and you are not the only one.
This creates a market wide contraction of sales aka a recession as the market endeavours to clear the government-induced bubble.
The government which created the problem blames greedy bankers and says it must intervene to prevent a crisis.
But government intervention only creates an even wider misallocation of capital by creating fake money aka inflating the fiat currency.
This creates an even deeper market-wide contraction of sales aka a depression and this is when things get really interesting politically.
Here endeth economics 101.
For more details see centre column free video lecture entitled-
The Financial Crisis: What Happened and Why
http://www.aynrand.org/site/PageServer?pagename=arc_financial_crisisLC