The "Replaces" field doesn't mean anything in the sense that it is for information only, to help a user figure out which course map is currently being used for a race. But when you think about it, the same is true for the "City" field.
I think though, that the "Replaces" field is redundant information. The certification number can be used to figure out the most recent map for a course. The most recent map is not necessarily the one currently being used for a race, but it usually is, and trying to determine that using the "Replaces" field isn't any more reliable.
So I kind of agree with Jay. Maybe we should stop using the "Replaces" field.