Accounting rules rarely garner much public attention, and for good reason: The business of toting up numbers is both devilishly complex and profoundly uninteresting to most Americans. This week, however, accounting was suddenly in the national spotlight as policymakers grappled with the ongoing financial crisis. At issue was a concept known as "mark-to-market." On Tuesday, the Securities and Exchange Commission (SEC), along with the Financial Accounting Standards Board (FASB)--the private regulatory body charged by the SEC with determining such arcane things--issued new guidance on how companies should apply mark-to-market rules to their balance sheets. It sounds like a small thing,...