From Instapundit (not just the link, but his comments):
CREEPY UNCLE SAM: FBI can turn on your Web cam, and you’d never know it. As I’ve said before, hardware on-off switches for cameras and microphones may come back into style. Plus this: “The FBI can also burrow into a suspect’s computer and download files, photographs and stored e-mails.” If they can do that, of course, they can also plant evidence without a trace. . . .