I imagine that in most cases when a user performs a search it makes sense to only search in live revisions.
E.g. when searching a web site's content that is maintained with edit-this-page, as you pointed out above ... this applies for most types of applications I guess. Even more so when there is no UI for the non-admin user to see the old revision - then it makes absolutely no sense to return a search result for that.
But then there are special cases when it might be useful to be able to search in all revisions, for example an editor that wants to search in old content.
Which makes me think that instead of deciding once per package which content gets indexed maybe rather all versions should be indexed and the code that actually performs the search should contain an option that decides if non-live revisions should be included in the search, defaulting to false.
(Just from the users point of view, I don't know if that would be feasible to implement.)
