The problem with being a blind ideologue is it seems to require disconnecting those areas of the brain responsible for reasoning and reading comprehension. Let's take a look at some of the sky-is-falling hyperbole in this thread, for example (paraphrased):
1. This penalizes fuel-efficient vehicles -- How so? Gas guzzlers still have to buy more gas than efficient vehicles. The more fuels efficeint your car, the less gas you buy, the more you save. Reducing or eliminating the gas tax in favor of a mileage tax doesn't change that.
2. Big vehicles do more damage, so they should pay more -- First, As Elfenix mentions and according to a study reported on the State of Oregon web site, heavy automobiles do NOT cause materially more damage than smaller autos. Large, heavy trucks (e.g., semis), however, do appreciably more damage and are already charged higher fees to compensate. In some states (e.g. Iowa), motor vehicle registration fees are based partly on weight, so heavier personal cars and trucks are charged more. I don't know how common that practice is. Finally, if it is determined that weight should be a factor for personal cars and trucks, it would be easy to charge a variable mileage rate based on vehicle weight.
3 MOAR TAXES!!!!! MOAR TAXES!!!!! -- The idea is replacing the existing fuel tax with a new mileage tax. I'm certainly not so naive as to think some governments won't try to take advantage of this, but they will be pressured by the same reactions that keep them from further raising fuel taxes. In fact, if this was implemented as a tax paid directly by the taxpayer (as opposed to something hidden in fuel prices as it is today), there would be greater pressure to limit the tax since it would be more visible. If it is implemented at the point of sale like the Oregon pilot, it would be more like the current gas tax.
4. This is more than an academic study. Oregon is pushing it. -- Not very actively, it appears. It may be somewhere on the Oregon governor's web page as the link above claims, but I didn't find it. It certainly isn't listed as one of his top priorities. Oregon did form a task force to study the idea and conduct a pilot (in 2003). As far as I can tell from their on-line records, this task force last met in 2004.
5. It's an invasion of privacy -- It certainly could be, and I agree that's a valid concern. Once we install tracking devices in all cars, no matter how benign the initial usage may be, it's only a matter of time before it is abused to infringe upon our right to travel freely without Big Brother's oversight. (By the way, Big Brother isn't limited to law enforcement. There are all sorts of business interests who would love to have that data: insurance companies, marketing groups, etc.) Unfortunately, we're moving more and more that direction anyway with the ubiquity of cellular devices and GPS, which is exactly why this idea was proposed in the first place.
6. Europe, libs, learning Chinese, and other stupidity -- Grow up or go outside and play. Your childish noise adds nothing and makes it difficult for adults to have intelligent discussions.
Personally, I think the basic concept bears consideration. We want roads, we need some way to pay for them, and a usage tax based on mileage seems to be a reasonable approach. Like the current fuel tax system, it focuses costs on the people who use roads most. Unfortunately, in order to make it practical, I think we would have to implement it uniformly at a national level, using a simple, cheap device already in every car ... an odometer. GPS seems too intrusive, too expensive, and too easy to game -- just block the antenna, especially before trips. I also think the Oregon approach of collecting the tax at gas stations is flawed. Alternative fuel vehicles like biodiesel and electrics will grow in popularity, creating more and more vehicles that never stop at gas stations. They need to pay their fair share, unless we decide to exempt them for other energy policy reasons ... at which point we should just keep it simple and stick to the current system of fuel taxes.
Cliff notes: Interesting potential in spite of the usual knee-jerk partisan hysteria, but significant practical and privacy obstacles to clear.