I think they spent too much time rebuilding the wheel(there own gis engine) and not enough on what services could make money. They could have easily used MongoDB or PostGIS as there engine and built there services on that.
The problem is that spatial data tends to create strange usage patterns compared to other software. I run PostGIS installs with tens of millions of features, most of which will never even be queried. Different spatial queries can result in dramatically different resource needs. I need a service that is affordable to store multi GB datasets, and can query them very quickly. SimpleGeo have not come close to solving this.
I checked SpacialDB page and it seems to be really good and useful for my essay, I want to use it to describe one of the three cases. Can you send me a beta invite, please? I registered there with this email: ricardo [at] fences [dot] com [dot] br
I'm working on a business startup project and this essay will be part of it, so I would like be a new customer when project start.
[edit] (ps.: I'm from Brazil. Feel free to contact me with that email.)