interesting points, though i have trouble seeing the logic in some situations.
do promises ever include caveats, such as?: " we will take you at #10, unless players x and y are available."
I think teams really only do it sparingly... maybe 1-2 teams a draft, if that.
And as others have said they only do it for a player they think could go higher if they worked out for other teams.
So, OKC may have seen enough in Cameron Payne -- if you believe the rumors they gave him a promise -- to put him something like 7th or 8th on their board when they're picking 14th.
They probably only issued him a promise if the other 6 are the consensus guys.... Towns, Okafor, Russell, Mudiay, Winslow, WCS (or someone else)... that they're fairly confident won't slip.
Teams also probably get some good will from teh player's agent b/c then that prospect doesn't have to work out for all the teams in the range they could go. From what i've heard the workout circuit prospects have to go through --- esp. say players in the late lottery and on --- is pretty gruelling (like a different city every day or every otehr day).
By the 4th or 5th stop a prospect could lose his legs, or just be worn down and news of a poor showing could spread.
So a team offering a prospect to not have to do that is a good thing for some prospects.
It also seems to add some intrigue to the player which also increases higher range interest in him... "who offered him a promise? why? what are we missing?..." Seems to be the case with Payne and IIRC Reggie Jackson 3-4 years ago.