or: meet TIM, POC and NIM
For the purpose of my dissertation it is more convenient to lay out the social software triangle this way (compared to this version)
It is a framework to position generic/abstract forms of usage of these tools. Of course I like it, when blogs are in the center, which also means that they are even more underdetermined than the other ones. Positions can (and will!) change by adding (or removing?) respective functionalities to the tools. E.g. adding widgets for social network awareness to wikis (based on co-authorship relations) will shift it into the NIM direction.
Other labels for the corners (counter clockwise, starting bottom left) could be: Organization of Knowledge, Communication of Knowledge(?) and Selections of Knowledge. For those from the KM tradition.