Excerpt: In a drive to cut costs, 401(k) plans are replacing familiar mutual-fund investment options with more-obscure vehicles known as 'collective investment funds.' Just like mutual funds, collective funds pool investors' assets and invest in stocks, bonds and other securities. The chief difference: Collective funds are typically available only in retirement plans. Because they aren't sold directly to the general public, they generally aren't regulated by the Securities and Exchange Commission.  MORE >>