Branches and all commits

Should *all* commits be reachable via at least one branch? I ran into a situation this weekend that has me a little confused. I had performed a number of commits and such and I noticed that the author and committer info had suboptimal values. A bit of searching led me to a comment made by Linus that basically said "go hack git-convert-objects", which I did. After performing git-convert-objects on every commit object in .git/refs/heads and the requisite pruning, etc... just about everything looked fine. However, I still had a long series of commits that contained the wrong information. Further inspection makes it appear as though these commits are not reachable via any branch, although they are /all/ reachable via a series of tags. I worked around the problem by further modifying git-convert-objects to also understand tags (at least the basic ones I've got) and that's all taken care of, but the question remains: should *all* commit objects be reachable by at least one branch?

-- Jon Nelson <jnelson-git@jamponi.net>