The critical media project is hosted on Gondor. It's generally been pretty smooth, but the documentation is a bit ad-hoc in places. I think they've been feeling out the PaaS thing at the same time as I have.
update nov 2013: uh, well, never mind. latitude is gone for good. the track your friends part of things has moved to g+, but a) no and b) there's no API anyway. i ended up rolling my own replacement using little fluffy location library for Android
The R script below tests whether a set of points on a plane is significantly clustered (as opposed to randomly distributed or, conversely, equally spaced), using the Clark-Evans R measure. From the R spatstat package manual "[Clark-Evans R] is the ratio of the observed mean nearest neighbour distance in the pattern to that expected for a Poisson point process of the same intensity. A value R>1 suggests ordering, while R<1 suggests clustering."
In late 2012, I spent an infinitely frustrating week trying to perform network analysis (specifically, build and run ergm models) on part of the bitcoin blockchain. I learned some things. If you are here because you want to run ergm models on large datasets, you're advised to back away slowly then run like hell. But here are some notes.