Thanksgiving Day had barely begun when Kevin Hofman’s BlackBerry buzzed. It was one of the technical operators of OnSmash.com, Mr. Hofman’s popular hip-hop blog, telling him that the site had gone mysteriously blank just after midnight.

“At first I thought it was hackers,” Mr. Hofman said. But within hours a notice went up on the site saying that its domain name had been seized by the United States Immigration and Customs Enforcement unit of the Department of Homeland Security; it was one of dozens of sites shut down, accused of copyright infringement and selling counterfeit goods.

But Mr. Hofman, a brawny Long Islander in his early 30s who formerly worked for a major record label, does not think of himself as a pirate.

OnSmash.com and the handful of other music blogs shut down by the government post brand-new songs and videos without licenses, but much of that material is often leaked to them by managers, music labels and even the artists themselves.