When I originally conceived of ThoughtStreams, it never occurred to me you'd want to re-order cards. My original thinking was that each stream would be a sequence of thoughts.
However, enough people seem to be interested in re-ordering cards that I'm giving it thought (although it will take quite a bit of thought, particularly from a UI point of view).
I think, personally, if I had things I wanted to re-order I'd make child streams for them rather than individual cards. But of course, re-ordering of child streams doesn't exist yet either.