(micro)payments for anonymous routing in Tor?

[tor-operator at sky-haven.net]

On Tuesday 23 September 2008 00:55:50 Josh Albrecht wrote:
> What did people think of this paper?
> cs.gmu.edu/~astavrou/research/Par_PET_2008.pdf
> 
> The basic idea is a scheme for micropayments between relays in the Tor
> network that does not create any new attacks on anonymity than already
> exist against Tor.  Obviously we wouldn't want a network that forced
> people to pay to use it, but maybe if relays gave slightly higher
> priority to payed traffic, it would be an incentive for more people to
> run relays?  (running a relay would earn you faster service from other
> relays, basically)
> 
> What are some other objections?  Would people be opposed to seeing
> something like this in Tor?

How do you pay anonymously yet have the system fairly permit "paid" traffic to 
have higher priority?  With anonymity intact, how do you audit and enforce 
this policy?