This new startup, Jet.com, is looking to be the Costco of the web, and to undercut Amazon's prices by an average of 10%. They won't focus on speedy 2 day "prime" delivery. Instead, by being a member and paying a $49 annual fee (like you do with Amazon or with Costco), you'll get access to discounts, but the products will take longer to ship to you. This is a great model for non-time-sensitive things, like re-ordering diapers.
But the best part of it is how they're building a pre-launch interest list: When you sign up, they give you a unique sharing code. For example, mine is https://jet.com/#/ji/cj2tx and I'm currently member 124,837 of 124,877 on their interest list. The more people sign up based on your code, the more rewards you unlock. That's not all that new or innovative -- but the part that's great is that they're offering lifetime memberships and even stock options to their top sharers. Which is a great marketing move, although the reality is that getting 100k options doesn't mean much unless you know how many total shares are issued, and what the strike price is. But it's marketing genius!