People will likely want more tools to work on MapStory with one another. Should investigate providing things like chat, wiki, issue trackers, etc. for their layers and maps.
This is talking about at the level of an individual map or layer. How do we form a community of people just working in depth on a single layer or set of layers of interest? For maps we'll likely see more of a copy and edit model, with lots of different mapstories. But for layers more tools probably make sense, things that let you collaborate with a number of people on editing that layer.