Several objections leap to mind. First of all, bandwidth is not limited in the way that roads are limited. In a WiMax-enabled, fiber-to-the-home future, it may well be unlimited. Second, users of bandwidth don't affect the rest of us the way that roadhogs do. Downloading "The Decline of the West" doesn't warm the globe, or wear out pavement, or make Manhattan any less agreeable a place to live or to stroll.
Third, and perhaps most important, roads are for the most part built by governments, using taxpayer money; networks are built by large telecom companies, which as we all know are greedy, evil, and mendacious. Abandoning net neutrality means siding with the likes of Verizon, something I don't usually do to say the least.
Taking those objections in reverse order: the airlines are greedy and mendacious too, but no one complains about them charging more for first class. The Electronic Frontier Foundation argues that the companies who build and provision networks shouldn't be able to charge what the market will bear. Umm, last time I checked we still lived in a capitalistic society.
"From a philosophical standpoint, network neutrality is to be strongly valued, EFF chairman Brad Templeton has said. "It's what built the Internet and made it what it is."
This is nonsense. What made the Internet what it is was corporate America discovering it could make money on it, and ordinary people a) realizing that the Web could improve their lives, and b) being willing to pay for it. The demise of net neutrality wouldn't change that; it would just require heavy users to pay more. That's the American way.
As for bandwidth hogs not harming others, well, I suppose you could argue that in some indirect, infinitesimal way the Spenglerophile is affecting my enjoyment by, say, making it harder for me to read "Doonesbury" online on a busy day. That argument might feel airy; but to the degree that service providers' costs are spread equally across all users, rather than being metered, I am affected.
In the real world, for now and for the next few years, bandwidth is if not scarce, at least not infinite. (This is especially true in the mobile world, where just watching a half-hour "Simpsons" episode sucks major RF capacity.) If the opposite were the case, how come the U.S. government expects to make between $15 billion and $20 billion in the upcoming 700MHz spectrum auction? I, for one, would rather the big carriers make their money charging premium prices to major-league bandwidth hogs instead of jacking up my monthly home DSL fee.
You could also hope that the extra revenues generated by traffic-prioritizing would go to, oh I don't know, actually improving the networks or bridging the digital divide or funding innovative R&D, rather than outfitting the oceanside villas of senior telco management. But then you could also believe the New York Knicks will win the NBA championship under Isiah Thomas.
All in all, the arguments for congestion pricing in cyberspace are less forceful than those in the streets. But that doesn't mean that net neutrality is a God-given right, or that service providers shouldn't be able to operate under the rules of capitalism.