I'm aware this has been asked before but I have a different suggestion. I don't believe that tagging is the answer to the version of SharePoint question. Why don't we simply have a dropdown checkbox list which allows the user to specify the version of SharePoint in question. Something like:
- SharePoint 2007
- WSS
- MOSS
- SharePoint 2010
- SharePoint Foundation
- SharePoint Enterprise
- SharePoint Online (Office 365)
etc.....