Among many patent reform proposals it is common to have a desire for better examination, and more detection of prior art and obviousness. But the patent office only has so much money for so many examiners.
So here's a simple solution. If you want to apply for a patent, you must put in some time, as an expert in your field, examining other patent applications, searching for prior art and giving opinions on the obviousness. Alternately, this duty could be given only to those who actually are granted patents, to make more sure they are "skilled in the art" of their fields.
Of course, such crowdsourced examiners would have biases. They would be expected to make a sworn statement about their biases. Making a false statement could have implications on their own patents as well as the usual penalties.
Those biased against the patent would mostly hunt for prior art -- in fact they would make the best hunters. Those unbiased could make better opinions of obviousness.
Like regular patent fees, this could be biased for small inventors. (Small inventors pay lower patent fees and get some better treatments.) Large companies might have to volunteer more time from their staff, or small inventors might get reductions in patent fees in exchange for good work. Peers would examine the work of other peers to keep them honest and to rate the quality of it. And of course, unbiased patent examiners and appeal boards would still have the final, objective say.
Other volunteers could also participate in prior art searches. But with the system described above, there should be no shortage of labour. And as the number of patents goes up, the system naturally increases the labour available to do the legwork.