1st, let me say, like Zack Kassian, I'm a fan of the concept of topic tags. However, unless they are used consistently - they are fairly useless.
The big benefit when used properly, is that when you click on a tag - all topics with that tag are shown.
My options are:
1. Get rid of them completely
2. Force at least one tag per topic (topic starter choice)
3. Force topic starter to choose from a list of predefined tags (this would make the best use of tags)
4. Allow choice of predetermined tags, but don't force every topic to have one.
5. Keep as is