The network is also getting almost 500 new members a week now, compared with roughly 200 per week pretty consistently for the last few months. We hit 17,000 members yesterday.
I sense that there may be increased visibility both of "Web 2.0" and "social networking" as more mainstream ideas, and of Classroom 2.0 as an easy entry point for both. I also wonder if it's being used at workshops or conferences as an example of how social networking can be productive for professional development. I'd welcome any other thoughts on what might be going on.