Here is an excerpt from the instructions for dismantling a Sturmey-Archer AW hub at sheldonbrown.com:
The right hand ball ring has a two-start thread and must be replaced in its original position, that position must be marked. String or adhesive tape may be attached to the spoke nearest to the letters “SA” which are stamped in one of the notches on the ring. The whole internal can now be withdrawn from the hub shell. (This is rarely a problem in practice.)
Okay - let's suppose, hypothetically, that one failed to mark the position as indicated here. When our unfortunate, hypothetical amateur mechanic goes to re-assemble the hub, how will he or she know that it was done incorrectly? What is the consequence of getting it wrong?