When shocks hit a fragile financial system, as in 2007 and 2008, the government has reason to guarantee the money market funds, as US authorities did. These implicit government guarantees attract more money into these financial channels from nonguaranteed channels, and more “hot money” flows into firms like MF Global, Lehman, and Bear via repo.
彻底堵上这一短期融资渠道是不行的，但凡事都得有个度。但脆弱的金融体系遭受冲击时（比如2007年和2008年），政府就有理由站出来为货币市场基金提供担保，美国当局正是这么做的。这一隐性政府担保吸引了更多的钱从无担保渠道流入了有担保渠道，导致更多的“热钱”通过回购协议流入了曼氏金融、雷曼和贝尔斯登这样的公司。