Anything is possible. I love the argument that Bitcoin is the currency of the under world. More guns, drugs, sex and other evil are paid for with the US Dollar, which is far more difficult to track.
I would not put it past the government or the NSA to create it in an effort to track money movement.
That said I don't believe that they did. If they did why did it take an accidental find (fake passports) to bring down Silk Road? If they have the ability to track, but don't use it in an effort to not let it out of the bag then what good is it?
Those are good questions. I was under the impression Silk Road was brought down by a mistake in a forum, but that's a side point. I have two possibilities and they aren't mutually exclusive. For this to take off in illegal activities it must look as though it will succeed in illegal activities. In other words...it has to work for awhile to gain momentum. Secondly, it isn't to a point to fully track yet. Sure, you can track addresses and make assumptions or occasionally link transactions. However, the systems will have to mature to connect all dots. That's where the classification as something other than a currency and the regulations associated comes in. One more note...you notice Ulbricht didn't spend much. He would have possibly been tracked had he.