I think Slashdot allows high karma users to disable advertising actually.
Re:Suspension, Ban or Hellban?
by bostonvaulter2 on Sunday June 05, 2011 @04:51AM
(#2621652)
Stackoverflow and sites actually do reduce the advertising in response to your level of karma.
The most valuable contributors would see little (or possibly no) advertising in exchange for the value they are contributing with their time. People who are disruptive have a cost and the compensation for that would be to gradually increase the level of advertising shown to them.
Clearly, this isn't perfect, but no system is and there is at least a rationale for it.