Please have a look at this question. When the question was asked by the OP, it had a scope related problem in the code snippet posted in it. 2 answers were posted for that question. But after the answers were posted, a friend of mine from Stack Overflow, edited the question(not sure with what intention) in such a way that the bug in the code was gone(it actually self answered the question). Please have a look at the question revision history, where I've rolled back the question to the original state, which has the problem in place.
My question is that, should such a practice be allowed/encouraged that an edit to a question renders all the answers posted for that question, totally irrelevant? As anybody who comes to have a look at the question later, will be highly confused as to why a question was asked without any problem and there were so many answers posted to it(not everybody cares to go through the revision history)? I happened to notice that, but not everybody would notice it.