im afraid its not this easy. continuing your stock exchange analogy, trading volume at the individual stock level will be too sparse and unevenly distributed to make an unassisted exchange workable except at massive unprecedented scale (which i admit we'll achieve eventually). that's why in daily deals "stock brokers" exist, they are groupon/LS/etc. and they're still bleeding cash trying to reach these merchants profitably despite their "high" gross margins.

also i dont think you've adequately fleshed out the chicken and egg problem; ie i dont think folks will sit there and load up their deal preferences without you having demonstrated some kind of value first. demonstrating that value will be difficult without reverting to industry standard stuff. back to square one.

most importantly, in daily deals merchants pay for marketing+distribution = new customers. what you're describing will mean the customers voting on a merchant will already be aware of that merchant, and this makes your pitch to them a different (and much more difficult) conversation. from the merchant's perspective, discounts lower their product's value in their customers' minds. imho the right way to deal with loyalty is through having a loyalty program (assisted by the many great startups in this business), not generalized discounting.

hope this helped.