I think the initial idea was that if somebody later came along and found some stale information, they could go in and fix it, the same way you do with Wikipedia

I think the initial idea was that if somebody later came along and found some stale information, they could go in and fix it, the same way you do with Wikipedia. Unfortunately, this vision of the site is at odds with the way Stack Overflow actually works, where each question has multiple answers that are upvoted, and one gets an "Accepted" checkmark from the asker. The solution that feels right is adding a new answer rather than stomping on somebody else's, but it seems unlikely that the new answer will get a lot of upvotes and even less likely that the asker will come back and reassign the checkmark. So a lot of more current answers are probably abandoned before they're even posted, and those that are posted end up buried (like the correct answer to that question, which is posted there but is currently languishing at 4 upvotes). Personally, I say that if you feel like an answer is outdated, you should either comment with a polite correction if you'd like the author to fix it or just edit in the updated information yourself. (This nets less karma than answering new questions, but I can say from personal experience that 150k karma and a dollar will buy you a pack of gum.)