there is a delay in getting it added to the blockchain.. but most of the usernames are spam generated from top twitter names.

Its full of spam names like @apple, @ladygaga, @wellsfargo and etc... here is a list from when it came in another thread a week ago: http://pastie.org/private/rkuws8thrzdkl1wumoo2vw its has a few users generating lists of top twitter handles to squat on.