Yep, tags are just for search engine optimization.

It actually makes a forum far more easily organized and searchable to tag. Tags are a good thing! If its your thread though, i am pretty sure you have the choice to remove the tags should you choose. Anyone can in most instances, edit all of the tags or add more.

For example, someone might tag this thread "tags" "blue tag" "searching the forum" and then someone who had the same question and did a search would easily find the answer.