Yup, the government should step in when private industry is either unwilling or unable to provide essential services at a reasonable cost, the keywords being essential and reasonable. Case in point roads.
The macroeconomic costs of having all roads be private would be huge. There would be a lot of lost productivity(not to mention fuel wastage) just on the collection of tolls. And of course anyone who owns property anywhere could find themselves at the mercy of a private interest who can essentially blackmail them by cutting off access to their home or business. Another example of an essential service where the government should, and in most rich places in the world, has intervened is insurance. The fact that the US pays so much more for getting so much less than countries with private health care systems has shown that private industry is either unwilling or unable to provide insurance at reasonable cost, and thus it must be taken away from them. Same with broadband, if US providers don't prove they are capable of *gasp* actually providing a decent service at a decent price then the government should step in. Broadband is in the new economy an "essential service", essentially the "roads" of the internet.
The classic straw man argument is of course "well then why doesn't the government run food stores? Everyone needs food!". While this is true, food retailing(not really going to go into production, which is a separate story) is actually one of the most competitive industries in the US. Competition forces companies to provide decent service at very low margins(1-2% in some cases). If the broadband industry were more like the food distribution industry then we wouldn't even have to discuss a government take-over.