That's actually a good idea. It's really frustrating how (in other types of news) a lot of buzz can be generated and then just silence and we forget it all and move on. But it's not really something that would sell well. Not many people care about yesterday's news, people want to know what's coming next and not what came out of some magazine's prediction several years ago.
It’s a great idea, but I doubt it would succeed. Human nature tends to include not admitting fault. Also, many readers seem to choose their news (at least political news) for confirmation bias (whether intentional or not), so a news site/paper saying they were wrong would defeat that.
Not saying that retractions don’t happen, but they seem to be always buried under the headlines.
That is something I considered. Many partisan sites love to point out the errors of the other side. I know Fox News loves to call out CNN all the time. However, if every site did it, I fear that would just lead to more confirmation bias. And why report that the other side was right? That hurts your viewpoint.
What we need is a non-partisan non-profit to do it. But then there’s the problem of funding (which results in conspiracy theories).
Seems like the best way now is for the reader to make notes to themselves and regularly check back to them and see how things changed, compared to where the hive mind was earlier.
Since we're talking about ideas for news services: I would love to be able to get a list of the most important news in a month or a year. Not a top 10 list but simply a way to try to catch up if you miss a few months.