Use case: user X creates a node and wants to give user Y the ability to edit the node as well. Think page administrators on Facebook. An Entity Reference field can be used to allow the node author to associate other users with the node, but how to provide edit rights for selected users?
A simple and common use case is a business directory website where Employee X creates a listing for Company Y and wants to allow Employee Z to edit the listing as well. There are several similar solutions out there but I've not been able to find a specific module or recipe for this common use case. Any ideas?