Or, you could be like the NSA. You could use the essentially limitless funds of the global bankers - via the U.S. borrowing system that maintains its status for borrowing from the banks because of the promise to repay through the IRS taxes of the people - to build a cubic mile or two of communications and computer equipment, including hard drives.

Then all you need to do is record and correlate all Internet communications, single out the ones that occur simultaneously with Bitcoin transactions showing up in the blockchain, and attach those to the correct ISP. This will, at least, give you the ISPs info about the bitcoin thief. If it is important to you, you might even locate his electronic position and hack his computer. If he has protected himself sufficiently from hacking, you will always be able to get a general, if not exact, physical location. You can send in your CIA comrades if he is foreign - former KGB if he is in Russian states - or the FBI if he is local (U.S.).

In doing this there is always the time lag in the gigantic NSA communications. But, currently communications worldwide are not sufficiently large to make this into much of a problem. As communications grow, as people use the Internet more and more, as more countries come online, the NSA will, of course, also be updating their abilities with the latest technology. And if they can get the first practical quantum computers that are built, they might actually be able to entirely control and reroute all communications without anyone knowing it. Actually, they are on the verge of doing this in some countries (the U.S.) now.

Next, taking over the world by coup. The NSA, the new world government. I wonder who really runs the NSA.