as for saying ghash is a 'dominant player'
the video shows that GHASH has 300k users.. thats 300k individual people. not one entity (but nice try with a ghost buster analogy)
i think you cant win this particular argument as ghash may have 300k users, but most of their hash power is provided by a very small number of users, most of whom are under the control or influence of ghash or bitfury.
you can see from the well analysed stats that ghash has several large entities mining with significant hashpower on its pool. ie: unlike the other 'so called public' mining pools, ghash has a small number of large entities (source: organofcorti)
AsicMiner claims to have about 5 Petahash on ghash (source: amhash)
Ghash itself seems to operate its own very large mining farm, and BitFury also has been known to have a large amounts of its own hash power on ghash (as well as its own separate mine). sources: reading between the lines of statements and conversations with ghash and bitfury.
bottom line is that ghash's hash power is quite centralised. its not worth trying to claim ghash is a prime example of decentralisation cos it isnt.
if ghash solely owned all its hashpower you would have a point. but if ONE of the large entities wanted to mess with the protocol, they would have to collaberate with GHASH to rewrite the mining protocol to change how bitcoin works.. BUT yes a big but to rebuttle your point.... the other 299 that actually give a crap about protecting the blockchain will move to different pools to then make GHASH's share of the hash power decrease.
for instance if ASICMiner colluded with GHASH to mess with the protocol. and maybe 10 other big players, totalling maybe 30 ptahash.. the other miners will move to take ghash's power away from ghash and move to other pools that stick with the standard protocols. making ghash's potential fork, redundant.
there is still no way for a single entity to control / alter the protocol. and even if there was, people can move to different pools and reinstate the standard protocol freely. there is nothing forcing people to stay, and also if peoples funds are at risk they have no reason to stay.
in short its far better to run a ethical service then try to attempt to mess with it