blottsie (3618811) writes with a link to the Daily Dot's "comprehensive analysis of hundreds of police raids and arrests made involving Tor users in the last eight years," which explains that "the software's biggest weakness
is and always has been the same single thing: It's you." A small slice:
In almost all the cases we know about, it’s trivial mistakes that tend to unintentionally expose Tor users.
Several top Silk Road administrators were arrested because they gave proof of identity to Dread Pirate Roberts, data that was owned by the police when Ulbricht was arrested. Giving your identity away, even to a trusted confidant, is always huge mistake.
A major meth dealer’s operation was discovered after the IRS started investigating him for unpaid taxes, and an OBGYN who allegedly sold prescription pills used the same username on Silk Road that she did on eBay.
Likewise, the recent arrest of a pedophile could be traced to his use of “gateway sites” (such as Tor2Web), which allow users to access the Deep Web but, contrary to popular belief, do not offer the anonymizing power of Tor.
"There's not a magic way to trace people [through Tor], so we typically capitalize on human error, looking for whatever clues people leave in their wake," James Kilpatrick, a Homeland Security Investigations agent, told the Wall Street Journal.