This feature request is a response to Anyone want to clean up some bad titles?
Two days ago, Björn suggested that we warn users when they post a new question with an identical title to an existing question. However, given that there are 10,881 question pairs with identical titles on Stack Overflow (hat tip M. Tibbits) as well as ...
... I suggest that we take it a step further.
Let's extend the heuristics for detecting—and blocking—low-quality questions to enforce unique titles, or at least flag new questions with duplicate titles automatically.
We can leave the precise heuristics of detecting a duplicate title up to the Stack Overflow development team. I have no delusions about the fact that a few questions will "slip through the cracks." The goal here is to be proactive about minimizing the number of duplicates, and I think that the best place to start is the existing heuristics for detecting low-quality questions.
After all, duplicate question titles are bad for a number of reasons: They often indicate a question that is itself a duplicate, but perhaps just as importantly, they decrease the signal-to-noise ratio when searching for questions. I honestly can't think of any reason that duplicate question titles are helpful, unless you are asking for a solution to the same problem in a different programming language. Even then, I think that it would be acceptable to rephrase the question to say "How do I do X in (insert programming language here)?"
Frédéric makes a good point about the potential problems with this solution:
I have a hunch that if we do that, people will find ways to circumvent it (changing case or punctuation, adding random spam), and we'll end up stuck in a an arms race.
We may get stuck in an arms race with some users, but I honestly think that many people new to Stack Overflow just don't understand the etiquette of asking questions here. If we could even convince people to rephrase their question more clearly 20% of the time, I think that it would be a tremendous boon to the community. Furthermore, remember that heuristics for low-quality questions already exist, arms race or no.