No one likes middlemen. So often, it seems they just add an unnecessary burden to transactions. So why are they necessary?
I was thinking about network topology the other day. When there are N people on one side (say buyers) and M people on the other side (say sellers), then of course there are N*M possible ways for them to talk with each other. But stick a middleman in there, and have buyers and sellers talk only to this middleman, and you’ve reduced the maximum number of communication channels to N+M.
How much is this reduction in complexity worth? Probably just about as much as the middleman will be able to charge. Also, add a few redundant nodes (competitors) for fail-over and extra bandwidth, and you’ve got yourself a nice little self-organized network architecture there.