I think it makes sense in the larger open data, open government world: there are a ton of people using GIS data who would like the ability to version control, branching or forks but do not benefit from the massive overhead and expense of commercial GIS systems and do not have significant development skills available to build something complicated.

Databases make the most sense when your data changes frequently but if you have something like congressional districts, census information, etc. where the data changes infrequently but is likely to be shared widely the DVCS workflow and simplicity are really appealing. Right now you could do quite a lot with e.g. a gh-pages branch which contains GeoJSON and a simple LeafletJS viewer to combine files into layers; being able to quickly preview data files just makes that easier and it seems unlikely that they won't be adding some sort of diff comparison feature in the future.