I think that people will end up having tags like 'Documents/Invoices/1998' to reflect a hierarchical organization that is otherwise unavailable with tags. This has already happened with the gmail label thing.
Furthermore, taking the reasoning as an extreme, unless there is a status symbol factor like for ios, to most having plasma or win8 as the tablet OS is probably just an implementation detail that should be completely hidden. All these 'plasma', 'active', 'okular', 'kontact', 'mer', 'calligra', 'maliit' keywords are things that the person using the device shouldn't have to care, they are confusing and to most they do not bring meaning nor content. Maybe software announcements should be passed through an indirection layer to hide them :-)