That article implies that the FBI might not have the private key to that address. It's very confusing. What did they seize exactly?
edit: They must have the key since the funds were moved today. IMO, this is bearish because newcomers to BTC will think that it can easily be confiscated. I'm surprised the private key(s) wasn't hidden better.
You have to remember that DPR was being watched for months, I suspect from about May onwards. The FBI are very crafty. They could have very easily broken in and put a key logger on his machine that he wouldnt detect. I bet the gov has many tools that arent available to the most savvy of hackers.. So, it would make sense that they would have a ton of info..
I was watching one of those FBI real life shows the other night on how they do pretty much what I just said. They would stage a car wreck to close off the street while their agents were in the house putting bugs, etc.. so, ulbricht goose was cooked probably by late spring...