A comment on the 'Dragonfly' urban skyscraper farm:
Like the urban farms that grew Avian and Swine Flu, this would be a concentrated petri dish for virii to mutate in. Thankfully, it would be a lot easier to isolate and destroy a rogue virus inside one of these buildings than on a bunch of scattered farms with no testing regimen - _if_ they have competent testing. It would be very embarrassing to grow the next lethal virus right inside the New York city limits.
What I wouldn't give to see one of these lit up from within by flamethrowers though.. one for our cyberwar future perhaps.