I don't know how much control you have with a belt trailer to dump into an auger.  I'm guessing that they unload way to fast for that application.  Mostly, I'd be afraid of the initial cost and the extra moving parts that would provide little benefit in most grain operations.  I know Jake runs some for litter (or at least he was looking into it) but for general grain farm use, I think the extra cost would definitely rule it out.

Be nice to have the dump, a belt trailer, a lowboy, and a flat bed or van for a nurse trailer, but kind of expensive.

Mike