I am thinking about an anonimity network (just as tor), but using some type of guarantee against mis-usage. For example, which torrent does: there is a tracker, which registers who has given how much how many pieces of a file, and uses this data to help or stop the actual downloader.
I am thinking about the same thing, but not with file pieces, but with network bandwidth.
Thus, you could get for example 1 gigabyte anonimized network traffic - but only if you give 1 giga for other somebody.
Does this, or something such this exist already?