The hci tag has been applied very rarely, almost certainly less often than relevant. What sort of questions should have this tag? My inclination is anything approaching usability/UX work from a scientific perspective is a likely candidate for this tag.
Generalizing it too much would risk making it apply to most everything on the site, so I think we should have a more formal process for determining what does/doesn't get the tag and toss that in the tag's description.
I think "formal process" is a scary phrase we should stay as far away from as possible for as long as we can.
The thing with UX is that it's so broad and so vague that often we find many similar terms that pretty much describe the same thing. Perhaps we should treat it more as a synonym than as its own thing. People searching for HCI on Google might intend to find questions that we happen to have labeled with interaction-design or something. I'd prefer for those people to find that kind of content than for us to become super-anal about which questions get which tags.
