I would like to be able to link in 3D DWFs into Revit, for a variety of reasons. The main one I'm going to point out here is to be able to intelligently link in something from Navisworks when you don't have access to the source file.
For ex: received NWC files from trade contractors, which while link-able in Revit, are basically useless in Revit; but Navis can export this to DWF, which Revit should be able to handle, but only does markup for some reason.
DWFs make good archive files, are used as locked files that still maintain all the smarts/geometry/sheets, many people use them to distribute content; it makes sense to be able to make use of all this as intelligent backgrounds in Revit. We can link RVT, DWG, IFC, DXF, DGN, SAT, SKP, point clouds, NWC/NWD (sort of), why not DWF?