[greymule]

Is this just so the umpire can potentially award more than one base?

Yes. BR had an easy double, maybe a triple, but tripped over F3 on the way to 2B. The ump can give BR 3B, not just the next base.

If the answer is yes, then if the runner is advancing, the umpire can award as he sees fit (one minimum or possibly more).

Yes.

If the runner is returning (and a play is not imminent) then the runner only gets one base.

Right. In Fed. But once again, many Fed umps, thinking OBR, do not award the next base.

If play is imminent, then either the runner is out when obstructed and tagged, or the runner stays at the base if he is obstructed yet manages to get back safely. Is that correct?

Not if he's obstructed, but if you judge the contact to be "incidental" and not obstruction, then yes. However, the benefit of any doubt goes to the runner, and the fielder has to make that play look awfully good. Honestly, I don't think I've seen it more than a couple of times in my life, if that.

I suspect that better wording than "imminent" would be "as the play is happening" or "in the immediacy of the play." If the ball isn't right there—if it's really still on its way—it's obstruction to me. I can see incidental contact occurring as a fielder covers a base and the throw draws the fielder into the path of the runner. If the runner made contact with the fielder just before the ball arrived and the fielder practically simultaneously caught the ball and made the tag, I'd probably call that an out. But it would have to be the throw drawing the fielder into the runner. Simply blocking the base before the runner got there is obstruction.

If the play happens to you, make a snap decision, and then call it and briefly explain it as if you're 100 percent positive, there's no doubt whatsoever in your mind, and there's nothing much to discuss.

Just edited a medical report by a major drug company in which they described the importance of their "eminent" product launch. If those doctors had read our rules books, they'd have known the word they wanted was "imminent."