People who oppose the use of markets in healthcare can point to two genuine problems: illness is extremely unpredictable, and it’s hard for a layman to tell the difference between good and bad treatment. I don’t think those problems are insuperable, but they’re certainly real.
Wait a second. If illness really is "extremely unpredictable," then we've got another reason to disbelieve Tim's earlier claim that asymmetric information is the main health market failure. After all, the whole problem with adverse selection is supposed to be that consumers can predict their illnesses, at least a lot better than insurers can.