The threat here isn't only proof that is acceptable in court: * Your actions could put you on a shortlist of people to be more thoroughly investigated. * Your

The threat here isn't only proof that is acceptable in court: * Your actions could put you on a shortlist of people to be more thoroughly investigated. * Your actions could tip off the people whom your information threatens; maybe they stop communicating with you (or worse) to shut off the leak. * Per the Snowden release, the NSA tracked the communications of people within something like 3 degrees of their targets. With standards that low, it's not a stretch to think someone would track everyone visiting the Washington Post's secure drop box.