You are making something that isn't that big of deal into a big deal. Now you think that they had the power to crash the markets? Half the users of bitcoins don't even know what mining is, so I don't think they would crash markets. Stop with this FUD.
If one mining pool gets 51% it would crash the markets. The users who didn't have an idea what mining was, would learn real quick. The press would pick up on it.
The problem here is that their pool fee is 0%. The guild faced this in the past year and they did the right thing. They increased their pool fee to drive people away.
Ghash.io will need to do the same shortly.