At least with Ghash they can't really gain much any longer from people moving to their pool at this point since they've already breached 50%. I mean they could, but at this point I have to assume they're not stupid enough to continue pushing their numbers in to the 50s. At least publicly.
Perhaps they did this before and it has paid off for them in the form of more people going to their pool. And now we're seeing these record numbers partially as a result of this attack? Maybe it worked too well?
What about something like this:
Here's another potentially likely GHash scenario:
- GHash sells most of its available bitcoins for fiat
- GHash achieves 51+% on purpose knowing it will trigger a selloff
- GHash buys back the bitcoins at a greatly reduced price
- GHash points its miners to other pools to alleviate the threat
- Bitcoin price rises again and GHash realizes a large profit from market manipulation
This seems like a low-risk strategy, generates a tidy profit for GHash, and can probably be done several times before the community catches on so long as they wait long enough between runups.
If you believe that they are so beneficent that they would never try anything like this, then perhaps you'd like to buy some shares I have in the Golden Gate bridge for sale?
In fact, when they point their own miners at other pools, they could (as you suggest) even be employing block withholding attacks to induce miners there to switch pools when the miners notice the luck is running below average or to force the pool operators to raise their rates in the case of PPS pools.