I forgot to mention that in regards to the large farms, they are certainly out there, those aren't just made up numbers or private mining software.

Here is the description of one such farm pushing nearly 7Gh/s

http://ethosdistro.com/farm/

There are others running ethos that I have seen with well over 50 rigs, so those high hashrates are achievable if you are willing to put in the time and make the investment, which as you might imagine is significant.