"How much are they willing to pay?"
"What does it cost to serve them?"
"Do they want to buy it from you?"
"How often will they show up?"
"How can you reach them?"
Your success in business will be determined by these questions.
But in reality, it's "How many people want what you're selling?" It's finding a market that has strong demand.
The reason people will share *your* product/service is they like the way *you* do it.
"Instead of trying to create demand, they're managing the huge demand." – @sivers
The next key to success is how you respond to that demand: what you offer and how you offer it.