As of the Snowden-leaked documents creation (so at least 2006-2009), the NSA was not, in fact, using that capability at all.
Nor was the FBI or DEA in a recent high-profile case against a certain Tor hidden website. Nor were international LEAs going after Freedom Hosting.
Also note that the final author on the Users Get Routed paper is Paul Syverson, inventor of onion routing and still an active Tor designer. Academic attacks are pretty common against Tor because Tor is the most serious and therefore most well-studied anonymity system. Most of them aren't feasible in the real world regardless of what the abstracts say.
Nor was the FBI or DEA in a recent high-profile case against a certain Tor hidden website. Nor were international LEAs going after Freedom Hosting.
Also note that the final author on the Users Get Routed paper is Paul Syverson, inventor of onion routing and still an active Tor designer. Academic attacks are pretty common against Tor because Tor is the most serious and therefore most well-studied anonymity system. Most of them aren't feasible in the real world regardless of what the abstracts say.