You can overstretch it as run it to the ground or others may try to apply something that isnt even near related.
The phrase explains itself: "stay were we get more return from our hardware." if that is ghash.io? btcguild? slush?.. If its the best for our return, thats where we need to be.
Pure and simple.
Sometimes you have to pull off the bandaid. If (not saying there's evidence) ghash is using their excessive hashrate to attack other pools, or to do double spends, or other nefarious activities, then it hurts bitcoin. News of such activities will drive the price of bitcoin down, which gives LRM less buying power for buying new hardware which hurts our returns in the long run.
If they aren't doing anything nefarious, then we should be able to get roughly the same return elsewhere.
If they are and enough people move their hashrate elsewhere then they won't be able to anymore.
I see no harm, and potential benefit to moving.