While I like the idea, I can see this as a problem too.
Those who want a peace of mind booking are probably running their flights on corporate accounts, are miles collecting or have established flight booking relationships. And price sensitive customers are most likely going to try finding the best deal themselves. Maybe the best way to solve that would be to give for 24h a best-price guarantee. Just for the "peace of mind" for the consumer - I am sure only a very low percentage is ever going to make use of it.
* Flying for the first time to Australia. Expedia gives you a price from Sydney to Perth for $500. Unbeknownst to you, there's a discount airline called "XXXXX" who does this leg for $150. Sure you could find it if you searched enough, but why not just pay $29 to crowd-source it? Most travel agents will not volunteer budget airlines, neither will many OTAs.
* You're flying from Buenos Aires to Toronto. It's Xmas and Kayak is quoting $1400. You can't find better anywhere and seats are disappearing fast. You put up a contest for $29 and an expert suggests booking to Ottawa and hopping off in Toronto to save over $400 each. They also suggest going to Montreal instead, paying $40 for a bus, and saving $900 each. Again, you could work this out yourself eventually, but why not just pay $29?
Consider these edge-case examples:
* You are relocating to another country but need to take your 3 cats. It will take you 5+ hours to find out exactly how to transport your cats. There are lots of regulations, especially when flying during winter. Why not just pay $29 and get someone who's flown with pets to save you many hours. (This is a real example from Flightfox.)
* You are flying with a group of 20 people from the US to Australia. You pay $29 and an expert gets in contact with an agent who has specific consolidated stock with an airline. You save $600 per person compared to the absolute cheapest price online. (This is a real example from Flightfox.)
Then of course there's premium class and using FF points. We've saved $5,000+ on exactly the same flights for business class travellers. Also, people don't realise the power of FF points. You can get RTW for 140k. But most people use 120k for simple return flights. If they do 2x return coach flights with FF points, they could almost have booked a RTW in _business class_ and flown many more segments than the 2 flights put together.
Those who want a peace of mind booking are probably running their flights on corporate accounts, are miles collecting or have established flight booking relationships. And price sensitive customers are most likely going to try finding the best deal themselves. Maybe the best way to solve that would be to give for 24h a best-price guarantee. Just for the "peace of mind" for the consumer - I am sure only a very low percentage is ever going to make use of it.