Federal reserve regulation D puts strict limitations on transfers from savings to ensure bank capital ratios and solvency, not liability.
Fraudulent withdrawals (eg: check forgery, ACH fraud) are caused by the nature of our high trust banking system.
Account takeovers are easiest to pull off via social engineering vectors.
Alternatively build a good key management UX and don't talk to any Nigerian princes. I'd rather prioritize that.
Bitcoin doesn't provide any protections in the case of your money being stolen, so it doesn't impose any limits.
Depends what you prioritise I suppose.