Not directly answering the OP's question, but I often contemplate this as well, but come to a conclusion based on my main purpose. When I am away on a trip/tour I am there first off for the tour itself (fill in whatever that means to you). I find that the more electronics I bring the more they start to lead the tour (as opposed to the riding, boating, kayaking, etc.). In other words, I concern myself with keeping them charged up (where is the next plug) or if blogging I am thinking of how what I'm experiencing will come across to my "readers." This can often take away from the moment to moment enjoyment of what I have originally set out to do - that is, tour.

In my mind, there should be a balance between the things we bring with us and what we are trying to accomplish. This goes for other items that we bring with us as well (unnecessary items that is).

After writing all that, I still like the idea of a dyno hub It's just unlikely that I'll build one into any of my wheels.

I do like to have a bright light for night-time riding, but with LEDs so efficient I can easily bring a few AAAs, or even stop at a store now and then and pick up a few new ones.