Since July 2010, Fannie and Freddie are trading in the OTC market, an illiquid market more easy to manipulate.
The webpage otcmarkets.com provides the data of short interest (they bet the stock will decline), 3 months average daily volume and days to cover if all that have a short interest decide to cover their position (purchase the stock on the open market to hedge the short-sale of the stock).

What is a Short Sale?
As defined in SEC Rule 200 of Regulation SHO, "The term 'short sale' shall mean any sale of a security which the seller does not own or any sale which is consummated by the delivery of a security borrowed by, or for the account of, the seller."

*As of October 31th, 2011. Freddie Mac common stock:
-Short interest: 27,223,227 shares
-3 months avg. daily share volume: 1,414,551
-Days to cover: 20 trading days, that is 1 month assuming the short-sellers purchase all the volume traded in the day.
Source: http://www.otcmarkets.com/stock/FMCC/short-sales
Assuming they buy 20% of the daily volume traded in order to not disrupt the market, they would need 100 trading days to cover, that is 20 weeks or 5 months to cover their position.

*As of October 31th, 2011. Fannie Mae common stock:
-Short interest: 30,396,086 shares
-3 months avg. daily share volume: 2,776,151
-Days to cover: 11 trading days, that is more than 2 weeks. But assuming they purchase only 20% of the daily volume, they would need more than 2 and a half months to cover.
Source: http://www.otcmarkets.com/stock/FNMA/short-sales

BOTTOM LINE.
The same politicians that now are outraged because Fannie and Freddie’s executives receive huge compensations while the enterprises are in Conservatorship, should introduce a bill to prohibit short-sales on the enterprises in Conservatorship.
Congress can’t allow investors to have a short-position on the taxpayer’s interest.

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