Seems similar to http://www.drawball.com/ , except that Moon requires registration while Drawball is anonymous. Ironic, considering the artists.
- Social login means sharing is only a click away, encouraging conversation and possibly more thoughtful contributions.
- We wanted to give people equal chance of contributing and avoid the scenario where a handful of users (vandals?) find the site before everyone else and take over it all. That meant limiting the number of marks a person can make in a given time period - and that's easiest to do when you have users.
Would love to hear your thoughts on these points. This is still a work in progress after all...