Zaarly's original buyer-centric, bountry-based product didn't work (and pivoted to a more traditional sellers model) http://pandodaily.com/2013/08/19/while-virtual-gigs-thrive-physical-gigs-die/ I remembered the good old Google Answers product (based on bounty) didn't work either? Even buyer-centric (request centric) services like Uber, Lyft, Sidercar ... etc ... use non-bounty based models. Have there been any buyer-centric, bounty-bases services that worked? e.g. "I'd pay $50 for ___ " ... "I'd pay $10 for answer to this question " ... etc thanks!
Buyer Centric on it's own may work if the value proposition is strong e.g. Odesk, elance , every Job board under the sun (in some ways), etc.
Bounty based though is intimidating because of the process of defining rates is arbitrary, in a non f2f interaction it's much easier to have a pre-defined set of rules to engage in.
But there is a classic problem of chicken and the egg problem in a buyer-centric marketplace and if one does not think it through, you may be in for a very long haul.
A big (maybe biggest) reason why buyer initiated bounty markets don't work is that the buyer is shouldering the initial cost and risk. They have to take the effort to *maybe* get a result, when they're the one trying to spend money and want to be as lazy as possible.
In contrast, if they go to a seller-driven market ("I will sell this for $50") then they know those opportunities are ready for their taking.
The markets where this works are the ones where the demand-supply balance is so wonky and/or so liquid that a buyer is sure to get responses from sellers. Examples would be oDesk/elance/99 Designs, where people post "I want to pay $100 for xyz."
You could count the stock markets too if you include bid-ask systems.