They track your contact with the advertising network as a cookie is only returned to its parent location.
One big conceptual jump for the lay reader seems to be that the page that you view as a unitary whole is actually composed of many discrete sources. One of these sources is the "web bug", transparent gif or banner ad or what have you. On totally different but similarly constructed pages, a component exists which is a bug returning to the same advertising network.
Therefore, the only sites you will be tracked upon visiting will be those which participate in the same advertising network. Ones which do not participate at all will not be tracked. I daresay that one concerned with revolution and/or sedition would not participate (although I'd be interested, and amused, by what advertising would be chosen to be shown on these sites.)
> Also, as a by-product of course, such devices would monitor the frequency
> of visits to left wing or marxist websites, which could be of interest to
Something like that is already on the rise. It's called "CARNIVORE", a network monitoring system which is located at the ISP or network concentrator. If the government wants to track your visits to pretty much anywhere in particular, or even build a profile of what you visit, it can. Web bugs have nothing to do with this; the web being a public network and ISPs being relatively easy to strong-arm have everything to do with this.
> know in macro economic terms the size of turnover of this market in
> information and its capitalisation? Is that what is keeping the internet
> going now in economic terms?
I believe that the internet (more specifically the world wide web), by and large, is still operating at a loss. We are still in a period of media consolidation. The most visible and the most visited sites make a small profit as a result of advertising; the vast majority cover their losses out of love or hope.
ISPs, OTOH, have always operated at a loss due to price competition. They're either turning into niche operations, where they deal mainly with higher-margin business customers, being bought up/going broke, or making a small profit by rationing service (customer service, technical service) and dealing in volume.
Marco
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> Marco Anglesio | Style and structure are the essence of <
> mpa at the-wire.com | a book; great ideas are hogwash. <
> http://www.the-wire.com/~mpa | --Nabokov <
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