Reuters says they're becoming much harder to get because the funding for them is running out. From the story:
Due to a last-minute rush of coupon requests, demand may exceed supply in the coming month, said the Department of Commerce official overseeing the subsidy program.
Rep. Ed Markey, a Massachusetts Democrat who asked for the update on the digital TV transition, said Congress may need to quickly pass additional funds in early January for the coupons. ...
The government program doling out $40 coupons to subsidize the converter boxes is likely to reach the $1.34-billion limit of its budgetary authority in the first week of January, said Meredith Attwell Baker, acting assistant secretary for Communications and Information at the National Telecommunications and Information Administration.
"Once the obligation ceiling is reached, the program will hold coupon requests until funds from unredeemed coupons become available," said Baker in the December 24 letter to Markey who chairs the House subcommittee on telecommunications and Internet matters.
"NTIA realizes that this would likely result in consumer confusion," she added. If the high demand continues at its current rate of more than 1.5 million requests per week, the agency could run out of coupons in late January.