I think the biggest trick is to move around, so it isn't as simple as getting a single address. Like with Bin Laden, a lot of the work was figuring out where he was. And Ross Ulbricht, maybe he wouldn't have been caught so easily if he changed hosters occasionally and the VPN had listed 100 internet cafes in different cities as connecting IP addresses instead of just 1. Certainly that's the way Tor works, always hopping around routers. It's maybe a bit pointless though, once they get your legal name it's pretty much a matter of time.