It would be great if we can query who all are following a particular tag. So something like this should be the query.
Select * from Users u inner join TagUserMap tum on u.Id = tum.UserId where tum.TagId = @tagId
Your underlying aim:
Just to know from whom can I expect answer on my question tagged with a particular tag which is not very much popular.
However, do not use this to create a list of people to harass to answer your question. That will lead to.... consequences ;p