I have studied credit derivatives for several years (as a researcher, see http://www.nek.lu.se/NEKHBY/Default.htm) and I have kept believing that these derivatives one day would be traded much more widely on exchanges, rather than over-the-counter. This is not, and has never been, obvious. Admittedly, exchange trading of credit derivatives has still not taken off but I think the current turmoil in credit should strongly support, if anything, more contracts going to exchanges rather than the opposite.
In my research I have mostly worked with contracts that are exchange traded (such as CDS indexes) and the reason for this is my belief that exchange-trading has a load of advantages, most notably the liquidity issue.
It will be interesting to see if the sub-prime crisis, which of course has hit the market for credit derivatives overall, in fact could be a blessing for those in the credit derivatives exchange business!