It seems a lot of questions on Meta Stack Overflow are being prefaced by "Feature Request:" or "Bug:". Should this title labeling be done, or is a duplication of the tagging system?
I think it's unnecessary at best. IMHO, if you need to prefix your title with "Feature Request:", your title needs more work - i should be able to tell. Same with bugs.
Rule of thumb: if it can be worked into a single sentence description of the post itself, then it should be. And if not, then it doesn't belong in the title at all.
I tend to preface a title like that because I think people use the title to work out how to vote and respond on a question, rather than the tags. The tags are a search convenience and I don't think most users review them before voting or providing comments and answers. The question content and its title are the most important when trying to garner responses, not the tags.