$2 Trillion of Retirement Money Lost in Economic Turmoil

I heard stories of people losing money from their retirement savings like IRA and 401K. Check out this article:

Pensions lose $2 trillion: congressional budget analysts - Oct. 7, 2008

$2 trillion?! Maybe a bloated figure. But I don't quite understand how retirement savings can lose value. My guess is that:

1. Inflation and decreasing dollar value decrease the value of retirement savings,


2. Financial institutions go under depleting money in retirement savings accounts, or


3. IRA and/or 401k can have assets like stocks as its basis and lose its value when the stock value plummets.

Anyway, here's an Washington Post article in which a finance Guru gives some good advices on dealing with the financial crisis.