I just saw a story a Bloomberg regarding Nobel Laureates Myron Scholes and Robert Merton's call for more accurate valuations on illiquid securities (http://www.bloomberg.com/apps/news?pid=20601109&sid=aiVPT2XgAgto#).
The problems with these assets came to a head last year when many holders of subprime mortgages had them on their books at inflated prices, but given their lack of liquidity had a challenge when trying to value them at more realistic prices. Last year Massachusetts Representative and chair of the House Committee on Financial Services, Barney Frank, suggested that institutions offer two prices: the listed one and what they thought was the more realistic one. I actually found this suggestion as having some merit, though implementing it would no doubt be quite difficult (from both accounting as well as procedural perspectives).
Whether FASB has the answers or not is unclear to me, but I suspect many firms would like guidance in this area.