What would that achieve? Members of a GB know what the equipment costs, they know the hash rate it should achieve, they know the current difficulty and they should know the hosting and pool fees, so they can calculate their estimated earnings fairly accurately (+/- a bit for miner variability). If a GB operator is sending out less than people expect it wouldn't be long before there are a lot of angry requests for explanations. I think a lot of hosters will be thinking of ways to demonstrate how the miners are performing (cgminer videos, visible pool profiles and payment addresses etc.) to maintain transparency.
You seem to be suggesting that somebody would want to buy a miner with GB money and mine for themselves while paying GB members BTC from some other source, but this only works as a scam if you pay people less than they deserve and pocket the difference. Since this is likely to be noticed quickly I'm afraid that your scam wont work
. Good luck thinking up the next one (sarcasm!)
