Nationalization also resolves the too-big-too-fail problem of banks that are systemically important and that thus need to be rescued by the government at a high cost to the taxpayer. This too-big-to-fail problem has now become an even-bigger-to-fail problem as the current approach has lead weak banks to take over even weaker banks. Merging two zombie banks is like have two drunks trying to help each other to stand up.
The JPMorgan takeover of insolvent Bear Stearns and WaMu; the Bank of America takeover of insolvent Countrywide and Merrill Lynch; and the Wells Fargo takeover of insolvent Wachovia show that the too-big-to-fail monster has become even bigger. In the Wachovia case you had two wounded institutions (Citi and Wells Fargo) bidding for a zombie insolvent one. Why? Because they both knew that becoming even bigger-to-fail was the right strategy to extract an even larger bailout from the government. Instead, with nationalization approach the government can break-up these financial supermarket monstrosities into smaller pieces to be sold to private investors as smaller good banks.