That is, nobody: they claim they have never received a request to not detect malware.

I think you need to look more closely at the list of companies and their locations in the second paragraph, and the list of companies that actually replied to the letter.

But we don't actually have to speculate about what the silence of the american companies means: they are quite open about their policies: http://slashdot.org/story/01/11/28/173201/symantec-will-not-...

>Symantec chief researcher Eric Chien stated that provided a hypothetical keystroke logging tool was used only by the FBI, Symantec would avoid updating its antivirus tools to detect such a Trojan, echoing a similar stance Network Associates allegedly took with its McAfee anti-virus software earlier this week. 'If it was under the control of the FBI, with appropriate technical safeguards in place to prevent possible misuse, and nobody else used it -- we wouldn't detect it,' said Chien. 'However we would detect modified versions that might be used by hackers.

Antivirus companies do not need government coercion not to detect malware. They do a pretty good job of that all by themselves.

The Illuminati. Come on. As a security researcher, you should know this. /s