But most of the bans are not retrospective. If government bans bitcoin today, it doesn't mean I will be prosecuted because government can track the trade I made yesterday. So unlike gold, I have a clear working plan if bitcoin gets banned. I can immediately send all my bitcoins into hiding using mixers. I can even sell them in disguise. All these features weren't present in case of gold so government could easily locate the person if he tried to sell gold in market. With bitcoins there isn't such problem.