YC can't replace the traditional corporation when the traditional corporation is the customer that buys their product.

The most successful (profitable) YC "products", Heroku, Dropbox and Airbnb, have very sound business models with tens of thousands of customers that are not "traditional corporations".

Heroku was acquired and is an excellent example of YC startups being the product traditional corporations purchase.

Is the fact that Heroku was acquired the rationale for calling it the 'product' purchased by 'traditional corporations'? If so, what threshold would you apply for when a company can be considered successful before it gets acquired? As companies of all sizes get acquired, aren't they all then 'product' that wasn't successful until a real company bought them?