Sound collections should be delivered with mappings for popular controllers, touchscreen devices have made it extremely simple to create custom and inspiring interfaces wich could be bundled with any digitally distributed sound set. And even dedicated hardware controllers have become very cheap, such as the Novation remote SL series providing xy pads, Pitch mod sticks and after touch (not polyphonic though) close enough together to control all of them with two hands (I think the Impulse with mod/pitch wheel is a step back).
The importance of a good controller mapping is very well illustrated by this video showing the use of an Haken Audio controller to control the sounds recorded earlier:
Amon Tobin's Making of ISAM sounds
It is not the sounds alone that make the magic happen, but the performance manipulating them afterwards.
This is the reason why I am looking forward to the future, at things like the Linnstrument. Or maybe we might even get a velocity and touch sensitive smartphone/tablet computer one day? Who knows, but today a simple mapping could lead to more interesting songs and productions. I think people who purchase sounds want to perform, not map or worse spend their time programming controller modulation behavior I hope someone creating a sound set right now finds this inspiring :)