He had something to do with Dave Winer's Userland Software - that developed early blogging software (Radio). Probably his biggest success, though, is his blog.
Because we don't know the traffic levels I can't say it is, for a fact, a success but Channel9 would probably be your answer. It was originally started by several 'softies but Scoble became the whole show and it stayed that way until he left.
Again, I don't have any traffic numbers but Microsoft still has Channel9 up and they still spends all that money on bandwidth so I have to assume it's considered a success to them.
What is Scoble's biggest industry success so far? Not career success; I mean, what's the thing he's best known for accomplishing?