some posts from last week mentioning the subject:
http://www.garlic.com/~lynn/2008k.html#1 dollar coins
http://www.garlic.com/~lynn/2008k.html#4 dollar coins
http://www.garlic.com/~lynn/2008k.html#9 dollar coins
http://www.garlic.com/~lynn/2008k.html#25 IBM's 2Q2008 Earnings
there was a reference to an interview given some time ago on the subject ... claiming that while its illegal, it was *safe* enough because "the Securities and Exchange Commission never understands this."
http://www.nypost.com/seven/03202007/business/cramer_reveals_a_bit_too_much_business_roddy_boyd.htm
update:
SEC Emergency Order Leads to Dramatic Drop in Short-Selling of Fannie Mae and Freddie Mac Securities
http://www.streetinsider.com/Press+Releases/SEC+Emergency+Order+Leads+to+Dramatic+Drop+in+Short-Selling+of+Fannie+Mae+and+Freddie+Mac+Securities/3840011.html
from above:
According to market statistics analyzed by S3 Matching Technologies, the SEC's emergency order to enhance investor protections against "naked" short selling in 17 financial institution securities has reduced short sells by about 70 percent for the targeted symbols, and 90 percent of short selling of Fannie Mae and Freddie Mac securities. S3, which processes trades for the country's largest brokerages, compared short sells of Monday, July 14, prior to the SEC order, and Monday, July 21, the first day the emergency rule was implemented.
... snip ...