Ouch, that sucks. Seems like there ought to be a way to detect this though, since you can't change the timestamps on solved blocks. Should be obvious if someone is holding blocks back consistently to implement this attack, no?
Although this is definitely off-topic, I think this is important enough to post everywhere.
I did my part and switched from BTCG to BitMinter. Although it looks like BitMinter is getting a LOT of stales recently. Strange. Is someone testing out this theory already?