What happens in a market where there are no buyers??

If a tree falls in a forest and no one is around to hear it, does it make a sound?
If there are no buyers in a market, will there be any prices?
We have not seen the end of the credit turmoil - check out the the interesting comments given by the CFO of Citi - some of his comments border on desperation and pure absurdity.
'No market to hedge CDO book' , 'No observable prices to judge prices', Citi is really in deep deep trouble here.
I am quite skeptical about our local banks as well - they did report holdings of CDOs on their books in August but Singapore accounting rules do not require them to mark these positions to market/model since these CDOs are held-to-maturity. The question is, if the underlying securities are marked down in ratings or have a higher risk of default, the cash flows from these CDOs will no longer be guaranteed. Expect more volatility ahead.