But again, you have to look at the alternative. A lot of people can't fully encrypt their hard drive or buy a separate computer, so they will be splashing evidence all over their hard drive. If a package gets intercepted and they get CDed (much more common than being identified through an attack on Tor), that evidence could screw them a lot harder than being identified by an attack on Tor as "a person visiting Silk Road". This is especially important for vendors, but even for buyers, unless you can memorize all your passwords, you will be splashing evidence on your hard drive.