A brief yesterday from The Economist explains why the IMF's Special Drawing Rights are not currency.
The SDR, a unit of account based on the US$, yen, pound, and the euro does allow countries to access real currency in hard times. The countries take on debt from the IMF in SDRs in exchange for currency. The SDR gained new attention late last month when members of China's central bank called for greater use of SDR in global accounting, displacing the US dollar as the standard reserve currency.
Yet as The Economist points out the SDR only really provides one of the functions of money: it's a unit of account. It's not currently a store of real value, since its essentially used to account sovereign debt, and it's not a medium of exchange. Even if you could get SDRs printed, you wouldn't be able to get your local McDonald's to take them as payment. In fact, unlike foreign currency, you wouldn't be able to find a McDonald's anywhere willing to take the SDR.
The Economist article also provides a chart that touches on another IMF issue. The injection of $750 billion proposed to the IMF at the G-20 last week will change the voting patterns of the organization. Votes are determined by funding and the new funds will re-balance this. I've copied The Economist chart to show that while the US losses a small vote share, that the UK, France, Belgium, and Russia are the big losers; they all lose more than 10 percent of their current share. Hence The Economist's chart title "Unfair."