A 40 GH/s farm isn't much more efficient than a 10GH/s farm. A 100 GH/s farm has no real economic advantage over a 40 GH/s farm.
not necessarily true. a company could create an ASIC and keep it to itself
this will be very inefficient for making a 10ghash farm, but could be better than FPGAS for 10terrahash farms
currently the total value of bitcoin isnt large enough to attract "big players"