The article (originally appearing on the web site Security Focus, a clearinghouse for computer security information) goes on to describe the way in which the FBI allegedly phrased the letters in an effort to intimidate the journalists in question.
By invoking the Ashcroft-popular Patriot Act, the FBI has threatened the recipients with criminal prosecution for even mentioning that they have received letters threatening them with prosecution for mentioning that they have received the letters.
The author reasonably points out that if the FBI was interested in preserving the information that the reporters had in their possession, all they needed to do was request it as part of an official investigation. Threats of use of the Patriot Act are unnecessary, because once the government asks you for something, destroying it is obstruction of justice. Even if it takes ten years to fight to have the documents (or email) handed over, the individual would be much better off preserving the documents and fighting the subpoena than destroying the documents for certain punishment for obstruction.
Now, remind me again, wasn't Mr. Ashcroft just telling us last week that he wouldn't misuse the provisions of the Patriot Act for anything other than terrorism? Maybe hacking is now terrorism. That'd be great, perhaps the folks in the middle east will get the word and attack each others computers instead of their citizenry.