I know this has most likely been covered before but if not:
Has the community considered implementing a system to "lock" old questions that already have answers to new users?
Honestly, I don't know why this is a issue but still every day the front page has at least a few questions that have been bumped by some new-ish ( <50 rep) user posting "their way" of doing exactly what the answer says on a old, more or less dead post.
I know that I'm new to meta and I may be over-stepping my bounds but I would suggest something like disallowing users with less then 50 rep to post on questions more then 6 months old with already selected answers (or at least ones that have been inactive for 6 months).
This would ensure we are not cutting off new user's options for posting too much as they can still post in active or unanswered questions and yet it would massively reduce that number of junk posts and necro'd questions.