The last time that Republicans actually shut down the government was during the Clinton administration. They were blamed for it, when President Clinton called the bluff of Speaker Gingrich and the Republican party.
Today, Republicans are threatening dire consequences if tax cuts for the rich are not preserved. Most of the financial consequences of the fiscal cliff can be undone after we "go over it" but it appears the only way to restore taxes on the top 2% of earners to the Clinton level is to let all current tax rates expire, by going over the fiscal cliff. Republicans refuse to negotiate in good faith on this point. President Obama must have the fortitude to see this through to the end game and call Republicans' bluff, if he truly seeks to restore balance to the income tax code.