Once a player buys a certain unit or item, that unit or item should stay. Taking it away looks like a bait and switch, which on the consumers end looks like fraud. If a consumer can't buy with confidence they won't buy. Which is what gree has done way too many times, and the reason I haven't bought gold in a long time. It doesn't matter if gree can take any unit away that players paid for legally, it what is perceived on the customers end that gree should be looking at.