Business
Piling up users is not the goal. What counts is having the right number of participants on each side who actually want to deal with the participants on the other side. Treating growth as a pure numbers game is a fallacy.
A business that connects two or more groups is worthless to each group until enough of the other group shows up. Every such matchmaker therefore needs a deliberate plan for climbing from almost nobody to the point where the network sustains itself.
When each group will only join if the other is already there, the way out is to win one side first and use it to attract the other. A dining-card business, for example, signed up restaurants before it went after diners.
Critical mass is often a local matter, because matches happen where people actually are. Platforms that try to launch everywhere at once spread too thin to reach it anywhere. Winning one place at a time works better.
A matchmaker's prices should depend on how much each group needs the other. They should not be set as if each side were a separate product judged on its own costs. Asking who needs whom, why, and how much decides who pays and how much.
It is common for one group to pay nothing, or less than its share of costs, because its presence is what draws the paying side. Losing money on one side can be the very thing that makes the whole platform profitable.
Correct prices are not enough. A platform must also set and enforce rules for how participants behave. Without good rules, bad conduct by some users drives away the others even when the pricing is right.
Once a platform succeeds, its pricing seems self-evident, but that is hindsight. At the start the right structure was not obvious, and many winners lacked a perfect plan and found it by adjusting along the way.
Many would-be platforms fail because they start from a clever technology rather than from a real problem two groups need solved together. Getting swept up in hype about a new tool leads firms to build connections nobody wants.