That means your round-trip run is only 100 feet so you can look at this chart (http://en.wikipedia.org/wiki/American_wire_gauge#Tables_of_A...) and divide the Ohm/kfoot by 10. If you used 4 gauge that would be 0.24 ohm/kfoot or 24 milliohms per 100 feet. 24 milliohms on 100 amps is 2.4 volts of droop or a 5% loss. Not awesome, but as an engineer, acceptable.
The 4 gauge is available in quantity for less than $1/ft. 1 gauge is available for about $2/ft neither of those prices are all that daunting.
If you lived on the ideal setup where you have neighbors on either side and off the backyard you could wire 6 houses together for less than $1000. Divided 6 ways that's $160 as a one-time cost to be able to be a lot less careful about your power usage. Hell everyone could net-meter with each other and settle up occasionally if someone's consumption got severely out of balance.
The thing that I really like about this (and which perhaps makes me overly optimistic) is that it would spur a lot of neighborhood engagement and re-forming of communities in the suburbs, which is somewhere that's severely lacking in a lot of places. Perhaps that desire is clouding my rationality; I can't say for sure. But I can say that with the population's general mistrust of large institutions growing by the year idea like this are going to look more and more attractive as time goes on.
https://www.google.com/search?q=millennials+distrust+institu...