Twitter is simple, easy, quick to pick up on and easy to use. Unfortunately, I can't imagine a public school firewall that wouldn't rotely block it because of the potential ramifications of its use. Ning would be another potentially great PLN to implement, but again, it was blocked by my school's firewall so I imagine that it would be by most others as well (our firewall is pretty liberal.)
I like the idea of my students creating a PLN within each classroom, but I worry that the limitations by firewall and then by the students that don't have access to the internet at home would hamper the viability of the program.
