If your company competes with Citibank, how can you win? Clearly the government has decided they are "too big to fail." Let's say you are a regional bank and you have made good decisions with your loan portfolio. In normal times, you would be the big winner and would be able to steal business from Citi. Now, everyone knows mistakes by Citi employees will be covered by the government. More importantly, Citi employees know it.
Let's say you are a loan officer at Citi. Compared to a loan officer at Regional Bank, you will be more likely to close that difficult loan.