It will always be the case (with Bitcoin) that specialization will tend make mining profitable only to a few and benefit from economics of scale.
This is only temperary due to the introduction of ASIC devices, soon ASIC devices will be everywhere and there will be no economics of scale (you pay more electricity to get more coins), just like early days of GPU mining, the most profitable ones are those have free electricity, those large mining farms typically have huge cost
This was only true before the existence of ASICminer meant that they can leverage their massive economicies of scale, essentially free electricity costs (compared to joe blow), and huge solomine hash power / extra hardware to control the market
They pay fractions of what you pay for
1. $ per TH/sec hashing power (they can setup 1TH/sec for less than 10,000$. Try to meet that anywhere else)
2. Electricity