You mean it's most relevant in binaries when people reveal the revision of a tool or module using a version command?
Well, perhaps that too. Main use is that it can be included in backtraces, as we do in Roxen. Would have to shorten the hashes, of course. (Gonna miss cvs' short revision numbers. Oh well, you can't have it all..)
In this case it'll work when they are in comments too.