Does the 16GH/s guestimate come from some kind of rough calculation? If so, based on what premises?

If it is plucked out of the air then il go back to lurking and let the rest of you FUD it out

Our chips in development
Generation 1: Fast-Hash. 28nm. Each chip's rated frequency is 800 MHz at 1.15V. It translates to 16,000 MH/s because it does 20 hashes per cycle. Chip requires proper handling of heat and power supply. It is expected the chip can be overclocked to 1000 MHz @ 20,000 MH/s.
eASIC Press Release