The 4th ammendment is meant to protect you from the power imbalance with the government. Or at least that&#x27;s how it seems to be interpreted by the courts.<p>Kyllo v. US ruled that heat-cameras mounted on helicopters were considered a &quot;search&quot; and could not be committed without a warrant because most people do not have heat-cameras and helicopters.<p>But everyone has ears (and microphones obstensibly work as well as ears in public spaces). The government has the right to investigate on the same level as normal citizens, in a way. Binoculars are also fair game, because a lot of people have binoculars.<p>The &quot;expectation of privacy&quot; is usually evaluated as &quot;if somebody could try to spy on me, would they be able to do so relatively easily?&quot;<p>In a way, this 4th ammendment interpretation is what protects us from NSA mass-surveillance. Because only very few people have the resources necessary to set up such a network, you can end up with an expectation of privacy.<p>And while you don&#x27;t have an expectation of privacy with regards to tor nodes (anybody running a node could be trying to watch you), IIRC expectation of privacy comes in if , as in the recent case, the gov&#x27;t runs a very large amounts of nodes and cross-references the data to &quot;find&quot; people.