Last year in this post I mentioned some research being done by Bala Iyer and Venkat Venkatraman at Boston University -- now at Babson College -- where they have been investigating ecosystems and multi-sided markets. A particular focus has become what is happening with the major online platform vendors and the mashup space. Last fall we setup a system whereby Bala could dynamically pull a subset of data from the Programmable Web database in order to run some numbers for his research.
Bala continues this research and the other day I took at look at his most recent graphs. Quite a bit more complex than the ones from last December. He has posted a whole series over the past year. In them, color is used to differentiate players (ex: Google is the dark blue), link thickness represents number of mashups made between two APIs, and size of circles represent number of mashups each.
It provides an interesting view into the mashup space and is a good alternate perspective to Programmable Web's mashup matrix which of course uses a grid representation rather than graph. Both are useful but in different ways.
More of Bala and Venkat's research can be found at their site Software Ecosystems.