Not allowing these companies that have grown too large, thereby choking out smaller businesses and other sources of innovation, to fail is something that will prove disastrous. If they aren't allowed to fail as they would naturally, it's like feeding the cancer in capitalism. Naturally, these companies would die off and make room for new and better companies to take there place, allowing for innovation and technological progression. That drive is stifled by keeping failed companies (cancer) alive. In the end all that happens is the government uses these monsters to their own ends through nationalizing them and sticking their fingers in where they don't belong.