Is it important for the seatpost clamp to be oriented with the cut in the seat tube? The reason I'm asking is because I have a frame with the cut on the front of the seat tube and I'd like to use a Surly cable hanger to hold my brake cable.

not a huge deal, sometimes i reverse them if the seatpost slips

The stock clamp on my Specialized TriCross actually has an arrow marking where the slot should be, which is on the opposite side to where the opening and bolt of the clamp are. Therefore, this reverse or offset orientation is apparently recommended in some situations. I'm assuming this distributes the force better, but I don't know the reason for sure. Anyway, go for it, it shouldn't cause any problem.

The slot got cut that way to keep muddy wheel spew from leaking down the seat tube, Its OK hang the clamp the other way.

the split tube will grip the seat post either way..