Nobody that I can remember has been able to identify the large bitcoin thefts over the years by tracking the coins, those people cashed out somehow. However the SEC filing on Pirateat40's ponzi scheme was remarkably detailed, they were able to track every single coin he received and prove he spent it on himself.
I would imagine others use JoinMarket to mix up the coins[1], use coin control[2] to exchange for other cryptocurrency p2p, or other obfuscation methods like buying up high demand items with bitcoin then selling them remotely for other bitcoins.
I would imagine others use JoinMarket to mix up the coins[1], use coin control[2] to exchange for other cryptocurrency p2p, or other obfuscation methods like buying up high demand items with bitcoin then selling them remotely for other bitcoins.
[1]https://github.com/JoinMarket-Org/joinmarket/wiki http://joinmarket.io/
[2]https://bitcointalk.org/index.php?topic=144331.0