True, but to exchange cash you need to either physically hand it over or have it delivered. If you exchange in person, then the other person will see you, and

True, but to exchange cash you need to either physically hand it over or have it delivered. If you exchange in person, then the other person will see you, and that person or a third party can capture an image of you which can be matched against a database of facial images. Identity blown, unless you're very careful to hide your face. If you exchange by delivery, by whatever method, your package can be tracked to either endpoint. Even if you use a courier, that courier knows the endpoints and can be coerced into revealing them, and also might be able to identify you or capture an identifying image of you. Again, it's very easy to lose your anonymity. It's all a matter of degree: the more likely it is that your transactions can be used as evidence against you (whether they're actually illegal or they're just being used as an intimidating force against you) the more you need to care about your anonymity. For most of us, most of the time, so long as we don't get creepy advertising that specifically references things we've looked at or purchased recently we don't really care about it.