I asked the following question on WebApps SE:
With Google Latitude closing down next month, this invalidates the correct answer to the question.
- Unmark the answer as correct and edit my question
- Open a new question stating "...without Google Latitude"
The first solution means the original answerer will lose 15 points, even though, at the time, they were correct.
The second solution means the original question will still be available to the public, when its no longer correct / helpful.
I believe the first solution would be best, but I think the original answerer deserves reward for their help.
Even if I remove the "answer mark" the user could start getting negative votes:
"-1 Google Latitude is no longer exists"