Comment by torginus

I had a friend who worked in telco as well, and he told me the reason why IP-based networking solutions will never completely replace earlier stuff like GSM is that the QoS algorithms used work extremely well in practice (which mesh networks prove), their behavior is completely nondeterministic, and tends to have really bad failure cases in overload, or certain nodes in the network failing.

Which means in SHTF situations (such as one when most people imagine this would be useful), these things tend to fail the most.