Shares of Bank of America dropped as much as 24% Thursday to an 18-year low following a Wall Street Journal report said that the banking giant would need more federal aid to complete its takeover of Merrill Lynch and as one analyst wondered if even that would be enough.

"Even with help from the government, we think BAC's tangible equity levels are low relative to peers," Standard & Poor's equity analyst Stuart Plesser said in a note. "It will need to cut its dividend and or raise equity capital in the coming months."