That was more a Microsoft thing, something to do with all accounts being able to access via 'public/shared folders, but you're right, depending on the administrator settings, program files are accessible to other users.  Besides, if WB (any SD skinning app) is made available to other users, the skins are accessible via the WB interface, so it shouldn't really matter where they are stored.

Having said that, however, it should be a consideration to dual/triple booters to have to option to store skins on a dedicated drive/partition and give all skinning apps the ability to select the skin path/folder, etc.  And it's not just a matter of space (of which I have ample) but rather that it's a pain in the arse when you do a full AV scan that has to inspect duplicated/triplicated skin files.  Damned AV thing takes forever... and to some, who are running average to lower powered machines, those resources used in this tedious process are invaluable if/when trying to do other tasks.

Yup, it has to be a consideration... registry edits, particularly for the inexperienced, should not be THE option.