That was my thinking as well, if two tags are named similarly enough that the slugify function generates the same slug for both of them (if a user happened to use the wrong capitalization, or punctuation, etc) I want them to be tagged the same. I'm basically using the slugify process to avoid having to do fuzzy matching (case/punctuation/etc differences) myself on the Name part. Since tags are about groups things together, erring on the side of collision seems preferable to me as well.