I realized that having a list of the component tags we used in Bugzilla might help jump start this effort, so here's the data I just pulled from Dre's backup, along with the number of times each tag appears to have been used (so we can consider which ones could be retired or split up):
no subject
APIs (RPC, XML, Flat): 63
Browser Issues: 28
Circle/Relationships: 41
Communities: 120
Crossposter: 101
Feeds: 42
Icons: 29
Importer: 76
Inbox/Notifications: 211
Invite codes: 34
Journal contents: 333
Misc Backend: 529
Misc UI/Frontend: 1303
Mobile: 5
Modernization: 188
OpenID: 29
Payments: 62
Registration: 25
Routing/TT: 67
S2 Backend: 109
Search: 55
Site Administration: 251
Site Layout/Navigation: 63
Style System: 923
Tags: 47
Testing: 13
Unknown: 80
Hope that helps!