(Rewritten - see the edit history for my original post.)
As we know, tags are used in the system to help categorise content by topic. People click on them to find more information about the same topic. So consider the user experience of someone that clicks or searches on the sharepoint-2007
tag, perhaps in conjunction with another tag like development
.
They find questions specifically about SharePoint 2007. Good user experience.
They never find questions tagged sharepoint-2003
, even though some functionality from that version works exactly the same in SP 2007. The OP using the SP 2003 tag had that version installed at the time so tagged their question with it, but have never used SP 2007 so don't know that their question applies in exactly the same way. Bad user experience.
They never find questions tagged sharepoint-2010
, even though some functionality from that version also works exactly the same in SP 2007. Again, the OP using this tag had their issue with the later version so tagged their question with it, without knowing the previous version behaved in the same way. Bad user experience.
This shows to me that version tagging doesn't help people find the information they want. In fact, it makes it harder. I have other issues with it as well such as duplicating the same content in multiple posts, causing problems with maintaining high quality.
It seems to me if we keep the version tags that the only way to make them work is have the community maintain them carefully. This means that every question needs to be checked on whether the version tag has been applied correctly. This is a massive workload (I've tried to do it since the site began and put 90% of my moderator time into it) that I think could be better put elsewhere.
My thoughts on a solution are to only allow one question without duplication for different versions - a "one stop" location for information about that topic. Answers to that question can cover the differing versions if necessary. In the rare case where a feature only existed for one version, the question title or content can always include the version if really required.
(Note: OP == "Original Poster". In the example, "original question asker".)