I have found a question about technology choice with regards to web developent, which is two and a half years old. I have tried to give it a bump, but since it has already been answered, I guess nobody will think about adding a new updated answer. I am relatively new here so I might not be in the possition to come with drastical suggestions, but could it be a good idea to turn all questions and answers that are more than two years old into community wikis? Maybe also that the answers need to be reconfirmed? I know this is really drastical, but the reason for this is that technology advances fast, which means that we will get a lot of correct, but obsolete answeres around.
Since you have enough rep, you can leave a comment at the answer mentioning your doubts. Or add a bounty (50 rep should be bearable if the answer is important for you) and leave a comment at the question stating you'd like to know if the accepted answer is still valid or a new one should be there.
NEW ANSWER -
I think instead of flagging as pointed out in below comments, you should leave a comment on such old obsolete answers/questions, so that other people can notice and act accordingly.
OLD ANSWER -
We do have flagging system in place to flag for moderator's attention if you see some answer or question is obsolete and not valid anymore.