the example law cited in the article would only apply a mileage tax to hybrids and electric cars. depending on the tax rate and miles driven this may make it cheaper to drive an electric car in the city than an suv into work from the suburbs.
the biggest concern i have with this is the tracking of cars. i already have to send in my mileage when i renew my registration every year, it would be simple enough to add a tax system to this. i do not like it one bit the idea of having a GPS tracking device in any vehicle i am in. sure they assure us they won't use it to track us, but once they have the ability to they will have "legal" recourse to track you with a warrant. and in the post-patriot act world, they don't even need a warrant anymore.