But private ownership can also have serious drawbacks. Transportation and communications services are essential inputs to a wide variety of industries. When the government helps a firm enter a transportation or communications market, it gives that firm a lasting advantage over potential competitors. If given free rein, a shrewd firm can leverage its government-supported dominance of a communications or transportation market to undermine competition and extract rents in adjacent markets that would otherwise be competitive. In the long run, this kind of rent-seeking behavior may prove dramatically more costly to consumers than would direct taxpayer support for the infrastructure.
via Keeping the Internet Competitive > Publications > National Affairs.