It's a regional thing. Up here in Washington State we'd be fools to not utilize the apple, cherry and apricot prunings that come out of the orchards. Fortunately, apple and cherry are excellent for pork and poultry. Cherry will give you a little more color than apple, so use it judiciously. I haven't used much apricot, but have liked what I've used. I'd like to try peach one day, but that's a southern thing that doesn't grow up here.
I pruned a neighbor's mulberry tree last year hoping to get to use the prunings for BBQ. Unfortunately, the thing was full of worms so I won't cook with it. I will say this, that mulberry was about the hardest, most dense wood I've seen grow around here. The sound from knocking two limbs together reminded me of the Brazilian rosewood used in xylophones. Seriously dense stuff that takes a long time to cure and would probably burn for a good long while in a smoker.