Similar to this question, but different reasoning:
And I feel like I have to ask a new question so that Jeff will notice.
Someone writes a question. Suppose it's a SQL one. They don't provide version information, so then I upvote an answer that runs nicely in SQL 2008. Then the question is edited to say it's actually SQL 2000. All I can do is put a comment on the answer I upvoted, saying that my upvote only applies because the code is fine in SQL 2008. But in the meantime, the answer that works on SQL 2000 is left languishing somewhere else, possibly never notice because the asker hasn't accepted it. So unless the person who Googles/Bings/Altavistas the solution notices the 15th comment where I write "This doesn't work on SQL 2000", and only notices the 100 upvotes (oh, sorry - I had said 'SQL', so that's not going to apply), the searcher is going to feel misled by this site.
So please, let me know if a question is edited (so that I can change my own answers), and so let me change votes if I feel it's necessary.