if even several people withdraw enough money, it will either go bust, like Lehman Brothers in 2008, or it's going to be bailed out with a loan financed with taxpayer money. And where will they get the money to repay the loan? By deceiving naive clients to buy bank products they don't need. So now that money they deposited that isn't really there, even that money gets depleted.
From what I understand of fractional reserve, the banks are obliged to keep a percentage of deposits in reserve while the remainder can be loaned out to other people, these loans would be sold out if there is a mass withdrawal;
• So, if I deposit $500 and the bank uses a 10% reserve policy, then $50 is stored in the bank while the remainder can be loaned out.
• If this is spread among 10 customers, the banks have $4,500 to give out while keeping $500 in reserve.
• The $4,500 which is loaned out incurrs an interest, this is the profit the banks make. If an interest of 5% annually is used, the banks should receive $4,500 + 225 = $4,725 at the end of the year. This could be split between 12 months at a rate of $393.75/month.
• The $4,500 loaned out is the liability the banks owe customer who deposited, while the $393.75/month loan interest is their asset.
In a situation where depositors withdraw more money than was kept in reserve, the banks would be forced to sell loans at a loss to other banks to raise money, this would not involve tax payers money.
During a synchronized bank run, or huge defaults on loans meaning losses for banks, they could fall back to the central bank as the
lender of last resort, more money could then be printed to keep banks afloat. Even though tax payers money is not involved, the system (which is a lot more complicated than this) is still flawed and has been plagued with a huge number of crisis over the years in many countries.
The decision to remove reserve policy could be an indicator of the situation in the economy; it's usually done to improve the money in circulation and to make loans available.
This could be one of the last cards the banks have to play inorder to salvage the economy, while putting them at high risk. So I would say, Yes, zero reserve policy is scary.