The morass of US child pornography legislation

According to a (now withdrawn) article posted at Salon, it is illegal for even law enforcement personnel to view "child pornography". This technically makes it very difficult to judge how prevalent this stuff actually is . . . and potentially dangerous even for members of the press to investigate:

Last month Debbie Nathan, an excellent investigative reporter whose work I've cited here before, wrote an essay for Salon about the legal barriers that prevent journalists and academics from double-checking government claims about the child pornography industry. You can still read the piece on Usenet, but it disappeared from Salon almost instantly. According to Nathan, the removal was prompted by legal threats from New York Times reporter Kurt Eichenwald, whose own investigations into "child model" sites were discussed in Nathan's article. In its place appeared a "correction" of questionable accuracy, written without Nathan's input or approval.