I was wondering the same thing myself today. My first argument would be that if data is getting into a black box, there's no reason it couldn't also get into a satellite transmitter and out into space in the same amount of time and with the same reliability. As for available bandwidth, how unrealistic is that bandwidth availability? How much data is being fed into a black box during a flight?

The idea of a distributed network among commercial aircraft and ground stations as a method of transmitting the data also seems like an exciting prospect, and perhaps less expensive than relying on satellite communications, though I know nothing of the range or viability of such a platform.

In any case, a system to complement a black box would require large expenditures by governments and airlines. But, how valuable is that data? Pretty valuable, I think.