I would believe if your friend told you that bitcoin can be hack, but to hack the bets in gambling sites by just a calculator? I think that is impossible. There a lot of codes that is being generated by the code generator that changes the winning pattern on every gambling site, so the possibility that your friend that can hack the bets on bitcoin casinos are only 0.00000001 percent.
Yes, since bitcoins is a digigal money stored on a digital money, bitcoins can be hacked anytime. Bitcoins already influence many people so i think bitcoins is strong now like a paper money. Although the government still have no right on bitcoins, bitcoins is already strong to manipulate virtual world. Bitcoins is very useful nowadays ao i think bitcoins is strong enough to compare with paper money.
Bitcoin has achieved a lot and from some kind experiment came to digital currency that is almost equal to paper money. It's not so strong like fiat but it's on the good way to become. Even some governments are aware thea Bitcoin has become an inevitable fact on the financial market so they are trying to grab some use out of it. But Bitcoin stil has battles to fight to get equal place like fiat money.