Have just read the tagwebs page (thanks Seth). For me, the problem with all the meta-tag structured data ideas (including tripletags in its current form) is in disambiguation of 'senses' of a tag. The tagweb idea plays out well until you have multiple meanings for the same tag. E.g. Phil and Phil (2 different people). Or Sleeper, Sleeper and Sleeper.
The big question is, how do you disambiguate a tag into its senses*? Can statistical analysis help?
(*without loosing the simplicity and serendipity of the system)