The average, "run-of-network" banner ad costs something like $6 CPM (cost-per-thousand impressions). That means that every time you look at a $6 CPM banner ad, the site you're looking at gets about $.006. Most banner-ad networks already do a lot of work to track users' movements accross sites, and to make sure that sites can't cheat the system by "earning" false impressions. It seems to me that the software that currently does that bookkeeping could pretty easily be modified to allow certain users to browse network sites without ads, charging micropayments against an established account instead.
The nice thing about this system is that it doesn't cost either the content-provider or the ad-server anything. They make the same money either way, since they can charge the same rates for banner ads as for micropayments. In fact, they can even charge different rates, if they want. I know that I would pay a premium to be able to 1) browse without ads and to 2) support my favorite sites directly. And since the payments are micro, a small account ($20) would probably last you a long time - I bet there are even ISPs that would front you this charge in exchange for switching to their service and for viewing their ads/whatever.
Another advantage of this scheme is that it changes the adversarial dynamic between advertisers and consumers. Instead of fighting with DoubleClick about my privacy, in a privacy vs. profits scheme, the ad-server and consumer are now partners, and the ad-server relies on consumer trust to survive. Since I personally don't trust DoubleClick with my privacy, I'd be much more disposed to take my micropayment account elesewhere.
Which leads me to my next point. It seems to me that it would not be that hard to develop an open-source distributed ad server that would allow sites to participate in this kind of scheme without paying a percentage of their profits to commerical ad-servers like DoubleClick. Besides the software, all that is needed is a trusted company to provide secure user accounts. They don't even need to charge anybody (users or sites) anything for this service, since they could make a decent amount of money the same way that PayPal does: accumulating interest on the money that they hold on behalf of their users. If every Slashdot/Freshmeat/K5 reader deposited $10 in their micropayment account, that would be a nice, tidy, profit. Then we can all start agitating for universal, cross-provider user accounts...
Anyway, that's my idea. I'd be curious to know if:
If this sort of thing already exists, and I'm just behind the times
Whether or not this is the kind of thing people in this forum are interested in. I occaisionally think up ideas like this, and I like to try and get feedback on them from an informed audience.