I see that many people creates new threads with multiple word tags like this "zimbra 8 spam issue". I think they should be created with 4 tags instead, like this: "zimbra", "8", "spam", "issue".
Without entering in the discussion of having tagged "zimbra" a thread opened in a Zimbra forum is useless or not (or even the use of "issue"), what I think could be improved is having a clarification when creating tags, saying taht they should be separated by "commas". At this time, there is no clarification of the separator needed when adding tags to a discussion.
This is (should be) a really easy change to make that will render the tags usefull again. Having multiple word tags kind of miss the point of actually having any tag at all i think.