It will be interesting to see this unfold. But I am inclined to believe Ulbricht here. My main reason for finding it immediately believable is that the name "Dread Pirate Roberts" is an obvious Princess Bride reference to a pirate who inherited his trade and occupation from another pirate. That combined with the fact that the name did not appear on the forums for the first few months leads me to believe that the name…
Despite all the evidence, lots of people did not want to believe it was him and held out for hope, in the end, though, people realized indeed it was he who did it.
[1] http://news.slashdot.org/story/08/06/09/1155214/hans-reiser-...
[2]http://yro.slashdot.org/story/08/02/23/2218256/hans-reiser-a...