"Evolution doesn’t just offer an escrow, but also takes advantage of a more advanced feature built into bitcoin known as multi-signature transactions. That feature is designed to prevent both scams and seizure of escrow funds by law enforcement. It requires two out of three parties—the buyer, the user, and the site itself—to sign off on a deal before the escrowed bitcoins can be transferred. Evolution has also had much faster pageload times than competitors, most of whom run painfully slowly thanks to Tor’s process of routing web traffic among randomly chosen computers around the world. (Just how Evolution managed those speeds despite running on Tor itself isn’t clear.) And it has been online far more reliably: The website Darknet Stats counts Evolution as online 97 percent of the time, compared with 83 percent for Agora and 93.5 percent for Silk Road 2 at last check in September.
I think the Achilles Spees of Evolution is how they arrive at these speeds because it may be that not all traffic is as TOR protected as is should or they have invested enormous money in SSL accelators and other hardware stuff on their servers.
The protection that is given to Bitcoin shows that not all bitcoins are equal and that some are even not that anonymous, it all depends on how they configurate it and that is something the receiver of bitcoins doesn't always has any control over.