Sometimes I run into answers that may have been correct at the time of answer, but could be wrong today. I ran into this more obvious post today, Mono on the iPhone? which says "there is no way to develop iOS from .NET" which is wrong today.
How do we/I handle this kind of answers?
In this case, answerers just put an answer or comment telling the latest news, which will be fine overall. The drawbacks is that the accepted marks on answers that aren't correct, and also that comments and answers afterwords may lead to poor answer quality because nobody (or few) monitor the question. I would see a alternate Flag that marks the question as Obsolete, old or maybe reviewing it like a sort of wiki where answerers/askers edit the query.