I am looking at the result of a svn->git conversion, and it is quite visible that quite a bit of the tagging in the svn repo has been done wrongly.
A tag should really only be done as a repo->repo copy, never from the wc. Now there are a lot of tags that are in themselves small branches, perhaps even in some cases containing changes that do not exist anywhere else. The result of this is that is not possible to re-create the svn tags as first-order citizens in a git repo, but that they must stay as branches. -- Lgb