Markets can't solve everything. If "the market" creates massive firms, maybe some things need massive central planning? See http://krugman.blogs.nytimes.com/2013/07/16/john-galt-and-th...
See: healthcare, finance, insurance.
Democratic accountability helps to keep the "parasite load" down, but only so much and only to the extent that problems capture the attention of the public (see again about the Department of the Interior). To the extent that the government does more stuff there's less democratic oversight on any particular thing that it does.